photomicrographs of iron and steel, reed
DESCRIPTION
Photomicrographs of Iron and Steel, ReedTRANSCRIPT
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PHOTOMICROGRAPHSOF IRON AND STEEL
PHOTOMICROGRAPHSOF
IRON AND STEEL
BY
EVERETT L. gEED, S.B.
Instructor in Metallurgy in Harvard University
WITH A FOREWORD BY
Dr. ALBERT SAUVEURGordon McKay Professor of Metallurgy and Metallography
in Harvard University
NEW YORK
JOHN WILEY & SONS, Ino.
London: CHAPMAN & HALL, Limited
1929
Tti
17H57
Copyright, 1929,
By EVERETT L. REED
Printed in U. S. A.
Printing Composition and Plates Binding
1. GILSON CO. TECHNICAL COMPOSITION CO. STANHOPE BINDESTBOSTON CAMBRIDGE BOSTON
23^
FOREWORD
It is with great pleasure that I comply with the author's re-
quest for a brief introduction to his excellent collection of photo-
micrographs illustrative of the microstructure of steel in its
many aspects. That there should be a need of such is an evi-
dence of the widespread interest taken in metallography. It is
of special significance to me and a source of gratification because
of the part it was my good fortune to play at a time when metal-
lography was indulgently regarded as a harmless and useless
occupation. That was in the early nineties — frequently mis-
named the gay nineties, if we consider the troubles we had and
our difficulties in overcoming the indifference, if not the hostility,
of the metallurgical world.
To the best of my knowledge the first photomicrographs of
steel taken in the United States were obtained in 1892 in the
laboratory of the Illinois Steel Company at South Chicago,
necessarily with scanty and crude equipment. All credit to the
late and much regretted W. R. Walker, at the time Manager of
the South Works, who had the foresight and the courage to di-
rect that the structure of steel be studied under the microscope,
following the methods described by Sorby in his masterful —epoch making — contributions to the Iron and Steel Institute
in 1886 and 1887 and the work which had then just been started
in France by Osmond and Le Chatelier and in Germany by
Martens. Let us sing his praise and rejoice that a steel metal-
lurgist lived at the time possessing the necessary imagination and
independence of thought to leave the ruts where others continued
to flounder. Walker took great interest in this study and was
satisfied with the progress made; it covered a period of about
four years, when a hurricane struck the South Chicago Works—in the form of a new president — which in its violence carried
away the metallographical laboratory and its occupants.
Following unsuccessful attempts to interest other steel makers
in the use of the microscope, I decided to continue the Work in-
iii
14-057
IV FOREWORD
dependently through the opening in Boston of some commercial
laboratories in 1896 and more especially through the publication
of a quarterly magazine, The Metallographist. The latter wasan audacious thing, as I look at it now in my more matured age,
for a young man to attempt single-handed. So many kind words
have been spoken, however, about the part played by this pub-
lication in creating an interest in metallography and in contribu-
ting to its progress that I am glad now that I did not have at the
time the wisdom and prudence to keep me from an undertaking
in appearance so hazardous.
Today, it is no longer necessary to justify metallographic
research. Indeed advance in metallurgy and even daily opera-
tions are now hardly conceivable without the use of the micro-
scope.
While we may look with some complacency on the work ac-
complished during the last thirty years, we realize also how muchthere is still to be done, how many problems are awaiting their
solutions, how much there is in the behavior of steel which re-
mains unexplained or but imperfectly understood.
Younger metallurgists have a large task before them, worthy
of their best efforts and promising of rich reward. It is in part
to help them that the author has prepared this set of representa-
tive structures. I welcome the opportunity it affords me of
placing on record the affectionate regard in which I hold the
author and my appreciation of his invaluable cooperation over a
period of many years.
Albert SauveurHarvard University,
August 16, 1928.
PREFACEThis little volume contains a set of photomicrographs of iron
and steels some of which have been subjected to mechanical and
thermal treatments according to standard practice. It is the
author's hope that they may prove of assistance to those inter-
ested in the production, in the treatment, and in the use of these,
the most important of industrial metals. The heat treatments
applied have generally been those recommended by the Society
of Automotive Engineers.
A list of iron and steels from which these photomicrographs
were taken is given below :—
1. Pure iron
2. Commercial iron
3. Wrought iron
4. Cast steel
(a) Annealed cast steel
5. Hot-rolled steel
6. Cold-rolled steel
(a) Annealed cold-rolled steel
7. A. Hot-rolled steel subject to recommended heat treatments
(a) Annealed steel
(6) Normalized steel
(c) Hardened steel
(d) Hardened and tempered steel
(e) Hardened and drawn steel
B. Hot-rolled steel subjected to the following miscellaneous
heat treatments:
(a) Steels heat treated according to the Metcalf test
(b) Graphitizing of cementite
(c) Spheroidizing of cementite
(d) Overheating and burning
(e) Grain growth in mild steel
8. Case-hardened carbon steel
(a) Heat treated case-hardened carbon steel
VI PREFACE
9. Decarburized steel
10. Alloy steel subjected to recommended heat treatments.
(a) Nickel
(b) Chromium(c) Nickel-chromium
(d) Chrome-vanadium
(e) Molybdenum
/) Manganese
g) Silicon
h) Silico-manganese
i) Chrome-tungsten
j) Non-scaling
11. Case-hardened alloy steel subjected to recommended heat treat-
ments.
(a) Nickel
(6) Chromium(c) Nickel-chromium
(d) Molybdenum(e) Chrome-vanadium
12. Nitrided steel
13. Gray cast iron
14. White cast iron
15. Malleablized cast iron
16. Semi-steel
17. Chilled cast iron
18. Cast iron containing special elements
In developing the structure, the following reagents were used:
A. FOR THE MICROSTRUCTURE
1. 5% Nital — for all carbon steels, cast irons, and some alloy
steels
95 cc. absolute methyl alcohol to which 5 cc. of concen-
trated nitric acid has been added.
2. 1% Nital — Preparatory to the use of Kourbatoff's Reagent
99 cc. absolute methyl alcohol to which 1 cc. of concen-
trated nitric acid has been added.
PREFACE VU
3. Kourbatoff's Reagent — High-speed Steels
4 parts hydrochloric acid
20 " iso-amyl alcohol
75 " alcoholic solution of nitro-aniline
4. Marble's Reagent — Stainless Steels
4 grams copper sulphate
20 " water
20 " Con. hydrochloric acid
5. Murakami's Reagent— Carbides and Tungstides in tung-
sten and high-speed steels.
10 grams potassium ferricyanide
10 '' potassium hydroxide
100 cc. water
6. Sodium Picrate — Cementite or Iron Carbide
2 grams picric acid
25 grams sodium hydroxide water to make 100 cc.
Cementite blackened.
B. FOR THE MACROSTRUCTURE
LeChatelier and Lemoine Reagent — to develop dendritic
segregation
10 grams copper chloride
40 " magnesium chloride (Increased contrast is de-
20 cc. hydrochloric acid veloped by washing off
1800 " water the copper deposit with
1000"
alcohol ammonia.)
The author is particularly indebted to Dr. Albert Sauveur,
Professor of Metallurgy and Metallography in Harvard Uni-
versity, for his valuable suggestions and for his kindly criticism
of the proof.
He wishes to express his warmest thanks to Dr. C. H. Chou for
the use of Figs. 4, 5, 32, 33 and 38; to the Ludlum Steel Com-pany for the use of information of nitrided steel, for the speci-
mens of nitrided steel and for the specimen of Seminole steel; to
Vlll PREFACE
the International Nickel Company for the specimens of cast ironscontaining special elements, and to Barbour and Stockwell Com-pany for the semi-steel specimen. Figs. 139, 140, 141 and 142were reproduced from Sauveur's Metallography and Heat Treat-ment of Iron and Steel, by permission.
E. L. REEDCambridge, Massachusetts,
June, 1928
CONTENTSPAGE
Temperature Conversion Table Inside front cover
Foreword by Dr. Albert Sauveur iii
Preface v
PHOTOMICROGRAPHS*
mONS
Pure IronFIG.
1. Electrolytic iron melted in vacuum— 100 X 3
2. Electrolytic iron melted in vacuum and annealed—100 X 3
3. Same as Fig. 2 — 500 X 3
4. Electrolytic iron drastically quenched showing Wid-manstatten or Martensitic structure — 100 X 4
5. Same as Fig. 4 — 500 X 4
Commercial Iron
6. Iron oxide in iron— 500 X 7
7. Iron sulphide in iron — 500 X 7
8. Iron sulphide in iron— 500 X 8
9. Sulphur print of high sulphur iron ingot (actual size) . . 8
10. Iron nitride needles in ferrite— 500 X 9
11. Iron nitride needles in ferrite — 500 X 9
12. Iron silicate in iron— 500 X '. 9
13. Sand grain in iron— 500 X 9
14. Aluminum oxide in iron — 500 X 10
15. Manganese sulphide in iron — 500 X 10
16. Commercially pure iron after cold working— 500 X . . 10
17. Commercially pure iron after quenching in water
from a high temperature — 500 X 10
* The magnifications indicated in this table are the original ones. The actual
magnifications used for reproduction are stated under each photomicrograph.
ix.
X CONTENTS^I«- PAGE18. Neumann bands in ferrite — 100 X 1119. Neumann bands in ferrite — 500 X 11
Wrought Iron
20. Longitudinal section of muck bar— 100 X 1521. Same as Fig. 20— 500 X
. 1522. Longitudinal section of wrought iron — 100 X 1523. Transverse section of wrought iron — 100 X 1624. Pearlite in longitudinal section of wrought iron
100 X 16
STEELS
Impurities in Steel
25. Manganese sulphide in low carbon cast steel — 500 X 1926. Inclusions in low carbon cast steel — 500 X 1927. Inclusions in low carbon cast steel — 500 X 2028. Manganese sulphide in screw stock — 500 X 2029. Titanium nitride or cyanitride in titanium treated
tool steel — 500 X 20
Cast Steel and Annealed* Cast Steel
30. Pipe in ingot — actual size 2331. Dendrite — actual size 2332. Macrostructure of a 0.52% carbon commercial cast
steel ingot — 2.5 X 2433. Microstructure of same as Fig. 32 — 100 X 2434. Macrostructure of same as Fig. 32, after drastic
annealing — 2.5 X 2535. Microstructure of same as Fig. 34 — 100 X 2536. 0.50% carbon cast steel, network structure— 100 X . . 2637. 0.50% carbon cast steel, network and Widmanstatten
structure — 100 X 2738. 0.50% carbon cast steel, Widmanstatten structure
-lOOX 2839. 0.50% carbon cast steel, network structure— 100 X . . 29
furna'"''^"^^''^'
heating steel above its thermal critical range and cooling in the
CONTENTS XI
FIG. PAGE
40. Same as in Fig. 39— annealed— 100 X 30
41. 0.35% carbon commercial cast steel — 100 X 30
42. Same as Fig. 41 — annealed 30
43. 0.85% carbon cast steel — 500 X 31
44. 0.85% " " " — 500 X 31
45. 1.10% " " " — 100 X 31
46.1.25%) " " " — 500X 32
47.1.25% " " " — 500X 33
48. 1.40% " " " — 100 X 34
49. Same as in Fig. 48, annealed 100 X 34
50. 1.40% carbon cast steel etched in 5% nital — 100 X . . 34
51. Same as in Fig. 50, etched in sodium picrate — 100 X 34
Hot-rolled Steel
52. 0.30% carbon steel finishing temperature near critical
range— 100 X 37
53-56. Illustrating the relation of microstructure to differ-
ent finishing temperatures in hot-rolled 0.50%carbon steel 37, 38
57. 0.85% carbon, hot-rolled steel — 500 X 39
58. 1.25% carbon, hot-rolled steel— 500 X 39
59. Banded structure in 0.50% carbon steel— 100 X . . . . 39
60. Banded structure in 0.50% carbon steel — 100 X . . . . 40
61. Persistent banded structure in 0.85% carbon steel —100 X 40
Cold-rolled Steel and Annealed Cold-rolled Steel
62. Cold-rolled 0.30% carbon steel — 500 X 43
63. Cold-rolled 0.30% carbon steel annealed at 550° C. —500 X 43
64. Cold-rolled 0.30% carbon steel annealed at 875° C. —500 X 44
Annealed Hot-rolled Steel
65. Annealed 0.08% carbon steel — 100 X 4766. Same as in Fig. 65 — 500 X 4767. Annealed 0.10% carbon steel — 100 X 47
xii CONTENTS
FIG. PAGE
68. Annealed 0.20% carbon steel — 100 X 48
69. " 0.30% " " — lOOx 48
70. " 0.50%) " " — lOOx 48
71. " 0.50% '' " — 500X 49
72. " 0.50% " " — 500X 50
73. " 0.85% " " — lOOx 51
74. Same as in Fig. 73, etched in 5% nital— 1000 x . . . . 52
75. Same as in Fig. 74, etched in sodium picrate — 1000 X 53
76. Same as in Fig. 74, etched in LeChatelier's reagent
— lOOOx 54
77. Annealed 1.10% carbon steel— 500 X 55
78. Annealed 1.25% carbon steel — 100 X 55
79. Same as in Fig. 78— 500 X 55
Normalized* Hot-rolled Steel
80. Normahzed 0.50% carbon steel— 500 X 59
81. Normahzed 0.85% carbon steel— 500 X 60
82. Normahzed 0.85% carbon steel— 500 X 60
83. Normahzed 1.25% carbon steel— 500 X 60
Hardened t Hot-rolled Steel
84. 0.08% carbon steel quenched from a high tempera-
ture— 500 X 63
85. 0.15% carbon steel quenched in water from 926° C. —500 X 63
86. 0.30% carbon steel quenched in water from 883° C. —500 X 63
87. 0.30% carbon steel quenched from a high tempera-
ture — 500 X 64
88. 0.50% carbon steel quenched in water from 840° C. —500 X 64
89. 0.85% carbon steel quenched in water from 800° C. —500 X 65
90. 1.25% carbon steel quenched in water from 776° C. —500 X 65
* Normalizing: Heating steel above its thermal critical range and cooling in air.
t Hardening: Heating steel above its thermal critical range followed by quench-
ing in a suitable medium, such as oil or water.
CONTENTS XUl
FIG. PAGE
Hardened and Tempered* Hot-rolled Steel
91. 0.85% quenched carbon steel — tempered at 400° C.
— 500X 69
92. 1.25% quenched carbon steel— tempered at 400° C.
— 500 X 69
Hardened and Drawn f Hot-rolled Steel
93. 0.30% quenched carbon steel drawn at 532° C. —500 X 73
94. 0.50% quenched carbon steel drawn at 600° C. —500 X 73
95. 0.85% quenched carbon steel drawn at 600° C. —500X 74
96. 1.25% quenched carbon steel drawn at 600° C. —500 X 74
Study of Transition Constituents According to the Met-calf Test
97-105. Represent a series of photomicrographs showing
the transition constituents of a bar of 0.50% carbon
steel heated to a very high temperature at one
end followed by quenching the entire bar in water
— 500 X 77-81
106-112. Represent a series of photomicrographs showing
the transition constituents of a bar of 0.85% carbon
steel heated to a very high temperature at one
end followed by quenching the entire bar in water— 500 X 82-88
113-124. Represent a series of photomicrographs showing
the transition constituents of a bar of 1.40% carbon
steel heated to a very high temperature at one
end followed by quenching the entire bar in water— 500 X 89-92
* Tempering: Reheating hardened steel to temperatures below the critical range
extending from room temperature to a maximum of 400° C. and cooled either in air
or in a suitable quenching medium.
t Dravying: Reheating hardened steel to temperatures above 400° C. — but belowits critical range— and cooling in air or quenching in a suitable quenching medium.
XIV CONTENTS
Spheroidized SteelFIG. PAGE
125. Partially spheroidized steel — 1000 X 95
126. Fully spheroidized steel— 1000 X 96
Graphitized Cementite
127. Graphitized cementite— 500 X 99
128. Graphitized cementite — 500 X 100
Overheated and Burnt Steel
129. Overheated 0.50% carbon steel — 100 X 103
130. Bmiit 1.25% carbon steel — 500 X 104
Grain Growth in Mild Steel
131. Grain growth in 0.08% carbon steel — Brinnell Ball
Test — 5.5X 107
132. Grain growth in 0.08% carbon steel — 100 X 108
133. Grain growth in 0.08% carbon steel — 100 X 109
Case-hardened Carbon Steel and Heat treated Case-
hardened Carbon Steel
134. Case-hardened 0.15% carbon steel cooled slowly after
carburizing— 0.85% carbon case — 100 X 113
135. Same as in Fig. 134 after recommended heat treat-
ment — 100 X 113
136. Case-hardened 0.15% carbon steel, cooled slowly after
carburizing— 1-40% carbon case — 100 X 114
137. Same as in Fig. 136 after recommended heat treat-
ment — 100 X 114
138. Phosphorus segregation in case-hardened steel—100 X 115
139. Case of normal steel — 50x 116
140. Case of abnormal steel — 50X 116
141. Hyper-eutectoid zone of normal case — 200 X 116
142. Hyper-eutectoid zone of abnormal case — 200X 116
Decarburized Steel
143. Decarburized 1.40% carbon steel — 100 X 119
CONTENTS XV
ALLOY STEEL
A. Nickel Steel— Cast, Forged, Annealed and after Recom-
mended Heat TreatmentFIG. PAGE
144. Cast nickel steel, 0.30%carbon, 3^%nickel— lOOX . . . 123
145. Hot-rolled nickel steel, 0.30% carbon, 3|% nickel—lOOx 123
146. Annealed nickel steel, 0.35% carbon, 3|% nickel—lOOX 123
147. Heat treated nickel steel, 0.30% carbon, 3|% nickel
— 100 X 124
148. Hot-rolled nickel steel, 0.30% carbon, 5% nickel —lOOX 124
B. Chromium Steel — Annealed and after RecommendedHeat Treatment
149. Annealed chromium steel, 0.40% carbon, 0.95%
chromium— 500 X 127
150. Same as in Fig. 149, heat treated — 500 X 127
151. Annealed chromium steel, 1.00% carbon, 1.35%
chromium — 500 X 127
152. Same as in Fig. 151, heat treated — 500x 128
153. Annealed stainless steel, 0.30% carbon, 12% chrom-
ium— 500 X 128
154. Same as in Fig. 153, heat treated — 500 X 128
C. Nickel-chromium Steel— Annealed and after Recom-mended Heat Treatment
155. Annealed nickel-chromium steel, 0.30% carbon, 1.75%nickel, 1.00% chromium— 500 X 131
156. Same as in Fig. 155, heat treated — 500 X 131
157. Annealed nickel-chromium steel, 0.35% carbon, nickel
3.50% chromium 1.50%— 500 X 131
158. Same as in Fig. 157, heat treated — 500 X 131
D. Chrome-vanadium Steel— Annealed after Recom-mended Heat Treatment
159. Annealed chrome-vanadium steel, 0.35% carbon,
0.95% chromium, 0.18% vanadium— 500 X 135
xvi CONTENTS
FIG. PAGE
160. Same as in Fig. 159, heat treated — 500 X 135
161. Annealed chrome-vanadium steel, 1.00% carbon,
0.90% chromium, 0.18% vanadium— 500 X 135
162. Same as in Fig. 161, heat treated — 500 X 135
E. Molybdenum Steel— Annealed and after Recom-mended Heat Treatment
163. Annealed molybdenum steel, 0.40% carbon, 0.95%chromium, 0.20% molybdenum— 500 X 139
164. Same as in Fig. 163, heat treated — 500 X 139
F. Hadfield Manganese Steel — Cast and after Recom-mended Heat Treatment
165. Cast manganese steel, 1.00% carbon, 12% man-
ganese— 100 X 143
166. Same as in Fig. 165 — 500 X 143
167. Same as in Figs. 165 or 166, after heat treatment —500X 143
G. Silicon Steel— as Cast
168. Cast silicon steel, 0.15% carbon, 4.50% silicon—100 X 147
H. Silico-manganese Steel— Annealed and after Recom-
mended Heat Treatment
169. Annealed sihco-manganese steel, 0.50% carbon, 0.75%
manganese, 2.00% siHcon — 500 X 151
170. Same as in Fig. 169, heat treated— 500 X 151
I. Chrome-tungsten Steel (High-speed) — Cast, Annealed
and after Recommended Heat Treatment
171. Cast high-speed steel, 0.60% carbon, 17% tungsten,
and 3.50% chromium etched in 5% nital— 500 X . . 155
172. Same as in Fig. 171, etched in Murakami's reagent —500 X 155
173 and 174. Other examples of cast high-speed steel
etched in Murakami's reagent — 500 X 155
CONTENTS XVll
FIG. PAGE
175. Annealed high-speed steel, 0.60% carbon, 17% tung-
sten, 3.50% chromium— 500 X 156
176. Same as in Fig. 175, heat treated — 1000 X 156
177. Same as in Fig. 175, heat treated — 1000 X 156
J. Special Alloy Steel — Possessing Properties of Hardness
and Toughness — after Recommended Heat Treatment
178. Seminole steel, alloy steel containing tungsten and
chromium annealed, — 500 X 159
179. Seminole steel, alloy steel containing tungsten and
chromium, hardened — 500 X 160
180. Seminole steel, alloy steel containing tungsten and
chromium, hardened and tempered — 500 X 160
K. Non-scaling Steel
181. Hadfield Era A. T. V. Alloy steel containing silicon,
chromium, nickel and tungsten— 500 X 163
Case-hardened Alloy Steels — after Recommended HeatTreatment
(1) Nickel Steel
182. Case-hardened nickel steel, 0.20% carbon and 5.00%nickel, heat treated — 100 X 167
(2) Chromium Steel
183. Case-hardened chromium steel, 0.20% carbon, and
0.75% chromium, heat treated — 100 X 167
(3) Nickel-chromium Steel
184. Case-hardened nickel-chromium steel, 0.17% carbon,
3.50% nickel, 1.50% chromium, heat treated —100 X 168
(4) Molybdenum Steel
185. Case-hardened molybdenum steel, 0.15% carbon,
1.50% nickel, 0.25% molybdenum, heat treated—lOOx 168
XVlll CONTENTS
(5) Chrome-vanadium Steel
FIG. PAGE
186. Case-hardened chrome-vanadium steel, 0.20% car-
bon, 0.95% chromium, 0.18% vanadium, heat
treated — 100 X 169
Annealed Nitralloy (steel used for nitriding; and
Nitrided Steels
187. Annealed nitralloy — 500 X carbon 0.36%, manganese
0.51%, silicon 0.27%, aluminum 1.23Sr, chromium
1.49%, sulphur 0.010%,, phosphorus 0.013%, mo-lybdenum 0.18%— lOOx '. 173
188. Nitrided nitralloy 173
189-193. Microstructures of the nitrided case as shown in
Fig. 183 — 500 X 174, 175
CAST IRONS
Gray Iron
194. Gray cast iron, no combined carbon — 500 X 179
195. Gray cast iron, no combined carbon, with steadite—500X 179
196. Gray cast iron, containing about 0.40% combined
carbon, with steadite — 500 X 179
197. Gray cast iron, containing about 0.60% combined
carbon — 500 X . 179
198. Gray cast iron, containing about 0.60% combined
carbon, with steadite — 500 X ISO
199. Gray cast iron, containing 0.85%, combined carbon
— 500 X 180
200. Gray cast iron, containing 0.85%, combined carbon
with steadite — 500 X 180
201. Gray cast iron, containing 1.25% combined carbon
— 500 X 180
Mottled Cast Iron
202. Cast iron, partially white and partially gray iron—500 X 183
CONTENTS XIX
White Cast IronFIG. PAGE
203. White cast iron— 500 X 187
204. White cast iron — 500 X 188
Malleablized Cast Iron
205. Partially malleablized cast iron— 500 X 191
206. Fully malleablized cast iron — 500 X 192
Manganese Sulphide in Cast Iron
207. Manganese sulphide in partially malleablized cast
iron— 500 X 195
Phosphide Eutectic in Cast Iron
208. Phosphorus eutectic in cast iron, etched in 5% nital
— 500X 199
209. Same as in Fig. 203, after etching in sodium picrate —500 X 199
210. Same as in Fig. 204, after heat-tinting— 500 X 200
Chilled Cast Iron
211-213. Represent a series of microstructures of sections
through a chilled cast iron specimen 203
SEMI-STEEL
214. Cast iron with eutectoid matrix, shown in Fig. 214 —100 X 207
215. Semi-steel with eutectoid matrix— 100 X 207
CAST IRON CONTAINING SPECIAL ELEMENTS
216. Gray cast iron, total carbon 3.16%, silicon 2.63%—100 X 211
217. Gray cast iron, total carbon 3.17%, sihcon 1.14%,nickel 2.83%— 100 X 211
218. Gray cast iron, total carbon 3.11%, sihcon 2.20%,nickel 1.11%, chromium 0.38%— 100 X 212
XX CONTENTS
APPENDIXPAGE
A. The Preparation of Metallographic Specimens 215
B. Etching Solutions for Microscopic Examinations
OF Steels and Irons 219
C. Microscopes 229
D. Photomicrography 232
E. Definitions 244
(a) Standard definitions of terms relating to Metal-
lography 244
(b) Definitions of other Metallographic terms 246
(c) Tentative definitions of terms relating to Heat
treatment operations 251
PURE IRON
Figs. 1-5 inclusive
PHOTOMICROGRAPHS OF IRON AND STEEL
PURE IRON
Fig. 1 Fig. 2
Fig. 3
Fig. 1. Electrolytic iron melted in vacuum. Large grains of ferrite. Etched in
5%Nital. 50 X. Original magnification, 100 X.
Fig. 2. Electrolytic iron melted in vacuum and subsequently heated to 1000° C.
for 15 minutes and cooled in furnace. Polyhedral grains of ferrite. Etched in 5%Nital. 50 X. Original magnification, 100 X.
Fig. 3. Same as in Fig. 2, more highly magnified. 250 X. Original magnifica-
tion, 500 X.
PHOTOMICROGRAPHS OF IRON AND STEEL
PURE IRON
Fig. 4
Fig. 5
Fig. 4. Electrolytic iron drastically quenched. Original austenitic grain bounda-
ries and martensitic structure. 50 X. Original magnification. 100 X.
Fig. 5. Same as in Fig. 4, more highly magnified. 250 X. Original magnification,
500 X.
COMMERCIAL IRON
Figs. 6-19 inclusive
PHOTOMICROGRAPHS OF IRON AND STEEL
COMMERCIAL IRON
Fig. 6
Fig. 7
Fig. 6. Iron oxide in commercially pure iron. Etched in 5% Nital. 250 X.Original magnification, ,500 X
.
Fig. 7. Iron sulphide forming continuous membrane around ferrite grains. Sul-
phur content, 0.62%. Etched in 5% Nital. 375 X. Original magnification, 500 X.
8 PHOTOMICROGRAPHS OF IRON AND STEEL
COMMERCIAL IRON
w
\,i>"i',^^w-^^
>^-/
^^"S". .Jy'
k^r y"
w. .-\\.
Fig. 8
Fig. 9
Fig. 8. Another example of iron sulphide in ferrite. Sulphur content, 0.62%.
Etched in 5% Nital. 250X. Original magnification, 500 X.
Fig. 9. Sulphur print of high sulphur-iron ingot. Sulphur content, 0.62%.
Actual size.
PHOTOMICROGRAPHS OF IRON AND STEEL
COMMERCIAL IRON
.a>
10 PHOTOMICROGRAPHS OF IRON AND STEEL
COMMERCIAL IRON
ty •
PHOTOMICROGRAPHS OF IRON AND STEEL
COMMERCIAL IRON
11
.\ ""W
WROUGHT IRON
Figs. 20-24 inclusive
13
PHOTOMICROGRAPHS OF IRON AND STEEL 15
WROUGHT IRON
Fig. 20 Fig. 21
Fig. 22
Fig. 20. Muck bar. Longitudinal section. Etched in5% Nital. 50 X. Origi-
nal magnification, 100 X
.
Fig. 21. Muck bar. Longitudinal section, showing duplex structure of slag.
Etched in 5% Nital. 250 X. Original magnification, 500 X.
Fig. 22. Wrought iron. Longitudinal section. Etched in 5% Nital. 50 X.
Original magnification, 100X
.
16 PHOTOMICROGRAPHS OF IRON AND STEEL
WROUGHT IRON
:-,
• - •^-;;^--!-:-7^'
IMPURITIES IN STEEL
Figs. 25-29 inclusive
17
PHOTOMICROGRAPHS OF IRON AND STEEL 19
IMPURITIES IN STEEL
Fig. 25
Fig. 26
Fig. 25. Manganese sulphide in low carbon cast steel. Etched in 5% Nital.
250X . Original magnification, 500 X
.
Fig. 26. An inclusion in low carbon cast steel. Etched in 5% Nital. 250 X.
Original magnification, 500 X.
20 PHOTOMICROGRAPHS OF IRON AND STEEL
IMPURITIES IN STEEL
Fig. 27 Fig. 28
Fig. 29
Fig. 27. Inclusions in low carbon cast steel. Etched in 5% Nital. 250 X.
Original magnification, 500 X.
Fig. 28. Elongated particles of manganese sulphide in screw stock material.
Carbon, 0.20%; manganese, 0.70%; sulphur, 0.11%. Etched in 5% Nital. 250X.
Original magnification, 500 X.
Fig. 29. Cubic crystal of titanium nitride or cyanitride in titanium treated tool
steel. The cubic crystal is pink in color. 250 X. Original magnification, 500 X.
Unetched.
CAST STEEL
AND
ANNEALED CAST STEEL
Figs. 30-51 inclusive
21
PHOTOMICROGRAPHS OF IRON AND STEEL
CAST STEEL
23
Fig. 31
Fig. 30. Photograph of a cast steel ingot cut longitudinally showing the pipe in
the upper part of the ingot. One-half natural size.
Fig. 31. Photograph of a crystallite, sometimes called a dendrite, a fir tree crystal,
or a pine tree crystal. These dendrites are found in pipes in castings. Actual size.
24 PHOTOMICROGRAPHS OF IRON AND STEEL
CAST STEEL
Fig. 32
Fig. 33
Fig. 32. Macrostructure of a steel ingot containing 0.52% carbon and 0.097%phosphorus. Dendritic segregation. Etched in LeChateHer's reagent. 1.7 X.Original magnification, 2.5 X.
Fig. 33. Microstructure of ingot shown in Fig. 32. Etched in 5% Nital.
Original magnification, 66.7 X.
PHOTOMICROGRAPHS OF IRON AND STEEL
CAST STEEL
25
Fig. 34
i^:i<^^^<^^.
c
*
"if'
Fig. 35
Fig. 34. Macrostructure of ingot shown in Fig. 32, after annealing one hour at
1000° C. Persistence of dendritic segregation. Etched in LeChateher's reagent.
1.7 X. Original magnification, 2.5 X.
Fig. 35. Microstructure of ingot shown in Fig. 34. Etchedin 5% Nital. 66.7X.Original magnification, 100 X.
26 PHOTOMICROGRAPHS OF IRON AND STEEL
CAST STEEL
Fig. 36
Fig. 36. Steel. Cast. 0.50% carbon. Large sorbito-pearlite grains surrounded
by a ferrite membrane from which occasionally radiates ferrite. Etched in 5% Nital.
50 X. Original magnification, 100 X.
PHOTOMICROGRAPHS OF IRON AND STEEL 27
CAST STEEL
Fig. 37
Fig. 37. Steel. Cast. 0.50% carbon. Large sorbite or sorbito-pearlite grains
surrounded by a ferrite boundary from which ferrite radiates, also some ferrite is
precipitated along the octahedral crystallographic planes. Etched in 5% Nital.
50 X. Original magnification, 100 X.
28 PHOTOMICROGRAPHS OF IRON AND STEEL
Fig. 38. Steel. Cast. 0.50% carbon. Slowly cooled through the critical range.
The ferrite is retained in the crystallographic planes. The structure is known as
Widmanstatten or cleavage structure. Etched in 5% Nital. 50 X. Original mag-
nification, 100 X.
PHOTOMICROGRAPHS OF IRON AND STEEL 29
CAST STEEL
Fig. 39
Fig. 39. Steel. Cast. 0.50% carbon. Network structure. Etched in 5%Nital. 50 X. Original magnification, 100 X.
30 PHOTOMICROGRAPHS OF IRON AND STEEL
CAST STEEL
Fig. 40 Fig. 41
Fig. 42
Fig. 40. Same steel as shown in Fig. 39 after annealing 5 hours at 850° C.
Grain refinement. Etched in 5% Nital. 50 X. Original magnification, 100X
.
Fig. 41. Steel. Cast. 0.40% carbon. Etched in 5% Nital. 50X. Original
magnification, 100 X.
Fig. 42. Same steel as shown in Fig. 41, after annealing 5 hours at 850° C.
Etched in 5% Nital. 50 X. Original magnification, 100 X.
PHOTOMICROGRAPHS OF IRON AND STEEL 31
CAST STEEL
Fig. 43 Fig. 44
Fig. 45
Fig. 43. Steel. Cast. 0.85% carbon. Lamellar pearlite. Etcheclin5% Nital.
250 X. Original magnification, 500 X.Fig. 44. Another spot on same specimen, the structure of which is shown in
Fig. 43. 250 X. Original magnification, 500 X.Fig. 45. Steel. Cast. L 10% carbon. Large grains of pearlite surrounded by a
fine membrane of cementite. Etched in 5% Nital. 50 X. Original magnification,
100 X.
32 PHOTOMICROGRAPHS OF IRON AND STEEL
CAST STEEL
^ r 7 'a
Fig. 46
Fig. 46. Steel. Cast. 1.25% carbon. Cementite partially rejected along cleav-
age planes and around grain boundaries. Etched in 5% Nital. 375 X. Original
magnification, 500 X.
PHOTOMICROGRAPHS OF IRON AND STEEL 33
CAST STEEL
Fig. 47
Fig. 47. Steel. Cast. 1.25% carbon. Cementite persisting around boundaries
of pearlite grains. Etched in 5% Nital. 375 X. Original magnification, 500 X.
34 PHOTOMICROGRAPHS OF IRON AND STEEL
CAST STEEL
Fig. 48 Fig. 49
Fig. 50 Fig. 51
Fig. 48. Steel. Cast. 1.40% carbon. Cementite between cleavage plane.s.
Etched in 5% Nital. 50 X. Original magnification, 100 X.
Fig. 49. Same steel shown in Fig. 48 after annealing 5 hours at 850° C. Cement-ite rejected to boundaries of pearlitc grains. Etched in 5% Nital. 50 X. Original
magnification, lOOX.
Fig. 50. Steel. Cast. 1.40% carbon. Cementite rejected to the boundaries
and separated along cleavage planes. Etched in 5% Nital. 50 X. Original mag-nification, 100 X.
Fig. 51. Same spot as shown in Fig. 50 after repolishing and etching in boiling
sodium picrate. The cementite is blackened.
HOT-ROLLED STEEL
Figs. 52-61 inclusive
35
PHOTOMICROGRAPHS OF IRON AND STEEL 37
HOT-ROLLED STEEL
Fig. 52 Fig. 53
Fig. 54
Fig. 52. Steel. Hot-rolled. 0.30% carbon. Correct finishing temperature,
namely, just above critical range. Etched in 5% Nital. 100 X.
Fig. 53. Steel. Hot-rolled. 0.50% carbon. Finishing temperature consider-
ably above the critical range. Etched in 5% Nital. 50 X. Original magnification,
100 X.
Fig. 54. Steel. Hot-rolled. 0.50% carbon. Finishing temperature consider-
ably above the critical range. Etched in 5% Nital. 50 X. Original magnification,
lOOX.
38 PHOTOMICROGRAPHS OF IRON AND STEEL
HOT-ROLLED STEEL
Fig.
Fig. 56
Fig. 55. Steel.
the critical range.
Fig. 56. Steel.
Hot-rolled. 0.50% carbon.
Etched in 5% Nital. 50 X.Hot-rolled. 0.50% carbon.
Finishing temperature just above
Original magnification, 100 X.Finishing temperature near the
critical range. Etched in 5% Nital. 50 X. Original magnification, 100 X.
PHOTOMICROGRAPHS OF IRON AND STEEL 39
HOT-ROLLED STEEL
Fig. 57 Fig. 58
Fig. 59
Fig. 57. Steel. Hot-rolled. 0.85% carbon. Sorbito-pearlite. Etched in 5%Nital. 500 X.
Fig. 58. Steel. Hot-rolled. 1.25% carbon. Sorbito-pearlite and traces of
cementite boundaries around grains. Finishing temperature near the critical range.
Etched in 5% Nital. 500 X
.
Fig. 59. Steel. Hot-rolled. 0.50% carbon. Banded structure. The light-col-
ored bands are rich in phosphorus and also contain many inclusions. Etched in
5% Nital. 50 X. Original magnification, 100 X.
40 PHOTOMICROGRAPHS OF IRON AND STEEL
HOT-ROLLED STEEL
Fig. 60
ift|MM|||8gB|A^gK
COLD-ROLLED STEEL
AND
ANNEALED COLD-ROLLED STEEL
Figs. 62-64 inclusive
41
PHOTOMICROGRAPHS OF IRON AND STEEL 43
COLD-ROLLED STEEL AND ANNEALED COLD-ROLLED STEEL
Fig. 62
Fig. 63
Fig. 62. Steel. Cold-rolled. 0.30% carbon. Deformed ferrite and pearlite
grains. Etched in 5% Nital. 375 X. Original magnification, 500 X.Fig. 63. Steel. Cold-rolled. 0.30% carbon. Annealed at 550° C. Equiaxed
ferrite grains and deformed pearlite. Etched in 5% Nital. 375 X. Original mag-
nification, 500 X.
44 PHOTOMICROGRAPHS OF IRON AND STEEL
COLD-ROLLED STEEL AND ANNEALED COLD-ROLLED STEEL
^*^^nM rite
Fig. 64
Fig. 64. Steel. Cold-rolled. 0.30% carbon. Annealed at 850° C. Equiaxed
ferrite and pearlite grains. Etched in 5% Nital. 375 X. Original magnification,
500 X.
ANNEALED HOT-ROLLED STEEL
Figs. 65-79 inclusive
45
PHOTOMICROGRAPHS OF IRON AND STEEL 47
ANNEALED HOT-ROLLED STEEL
s
48 PHOTOMICROGRAPHS OF IRON AND STEEL
ANNEALED HOT-ROLLED STEEL
Fig. 68 Fig. 69
i
Fig. 70
Fig. 68. Steel. Annealed. 0.20% carbon. Ferrite and pearlite grains. Etched
in5%Nital. 100 X.
Fig. 69. Steel. Annealed. 0.30% carbon. Ferrite and pearlite grains. Etched
in5%Nital. 100 X.
Fig. 70. Steel. Annealed. 0.50% carbon. Pearlite grains surrounded by a
membrane of ferrite. Etched in 5% Nital. 100 X.
PHOTOMICROGRAPHS OF IRON AND STEEL 49
ANNEALED HOT-ROLLED STEEL
Fig. 71
Fig. 71. Steel. Annealed. 0.50% carbon. Ferrite surrounding grains of sorbito-
pearlite. Etched in 5% Nital. 375 X. Original magnification, 500X
.
50 PHOTOMICROGRAPHS OF IRON AND STEEL
ANNEALED HOT-ROLLED STEEL
Fig. 72
Fig. 72. Same steel as shown in Fig. 71. Ferrite and pearlite. Etched in 5%Nital. 375 X. Original magnification, 500 X. ^
PHOTOMICROGRAPHS OF IRON AND STEEL 51
ANNEALED HOT-ROLLED STEEL
Hi
52 PHOTOMICROGRAPHS OF IRON AND STEEL
ANNEALED HOT-ROLLED STEEL
Fig. 74
Fig. 74. Steel. Annealed. 0.85% carbon. Lamellar pearlite. Etched in 5%Nital. 750 X. Original magnification, 1000 X.
PHOTOMICROGRAPHS OF IRON AND STEEL 53
ANNEALED HOT-ROLLED STEEL
Fig. 75
Fig. 75. Same spot as shown in Fig. 74, after repolishing and etching in boihng
sodium picrate. The cementite in the pearlite is blackened. 750 X. Original mag-nification, 1000 X.
54 PHOTOMICROGRAPHS OF IRON AND STEEL
ANNEALED HOT-ROLLED STEEL
Fig. 76
Fig. 76. Same spot as shown in Fig. 75 after repolishing aiul etching in
LeChatelier's reagent. 750 X. Original magnification, 1000 X.
PHOTOMICROGRAPHS OF IRON AND STEEL 55
ANNEALED HOT-ROLLED STEEL
'j^^^^-^'{'r^-^
Fig. 77 Fig. 78
;*.<" ^V
Fig. 79
Fig. 77. Steel. Annealed. L 10% carbon. Lamellar-pearlite grains surrounded
by a fine membrane of cement ite. Etched in 5% Nital. 250 X. Original magnifi-
cation, 500 X.
Fig. 78. Steel. Annealed. L25% carbon. Pearlite grains surrounded by a
membrane of cementite. Etched in 5% Nital. 100 X.
Fig. 79. Same as in Fig. 78. More highly magnified. 250 X. Original mag-nification, 500 X.
NORMALIZED HOT-ROLLED STEEL
Figs. 80-83 inclusive
57
PHOTOMICROGRAPHS OF IRON AND STEEL 59
NORMALIZED HOT-ROLLED STEEL
Fig. 80
Fig. 80. Steel. Normalized. 0.50% carbon. Grain.s of sorbite .surrounded bya membrane of ferrite. Etched in 5% Nital. 375 X . Original magnification, 500X
.
60 PHOTOMICROGRAPHS OF IRON AND STEEL
NORMALIZED HOT-ROLLED STEEL
Fig. 81
Fig. 82
mmmm
HARDENED HOT-ROLLED STEEL
Figs. 84-90 inclusive
61
PHOTOMICROGRAPHS OF IRON AND STEEL
HARDENED HOT-ROLLED STEEL
63
Fig. 84
Fig. 85
;JMMW|\^^^^ffi^^
64 PHOTOMICROGRAPHS OF IRON AND STEEL
HARDENED HOT-ROLLED STEEL
Fig. 87
rt«
PHOTOMICROGRAPHS OF IRON AND STEEL 65
HARDENED HOT-ROLLED STEEL
HARDENED AND TEMPERED HOT-ROLLED STEEL
Figs. 91 and 92
67
PHOTOMICROGRAPHS OF IRON AND STEEL 69
HARDENED AND TEMPERED HOT-ROLLED STEEL
Fig. 92
Fig. 91. Steel. 0.85% carbon. Heated to 800° C. and quenched in oil; tem-
pered at 400° C. and quenched in oil. Troostite. Etched in 5% Nital. 500 X.
Fig. 92. Steel. 1.25% carbon. Heated to 776° C. and quenched in oil; tem-
pered at 400° C. and quenched in oil. Troostite. Etched in 5% Nital. 500 X.
HARDENED AND DRAWN HOT-ROLLED STEEL
Figs. 93-96 inclusive
71
PHOTOMICROGRAPHS OF IRON AND STEEL 73
HARDENED AND DRAWN HOT-ROLLED STEEL
Fig. 93
Fig. 94
Fig. 93. Steel. 0.35% carbon. Heated to 912° C. and cooled in air; reheated
to 842° C. and quenched in water. Drawn at 532° C. and quenched in oil. S. A. E.
Steel No. 1035 after recommended heat treatment VII. Sorbite. Etched in 5%Nital. 500 X.
Fig. 94. Steel. 0.50% carbon. Heated to 850° C. and quenched in oil. Drawnat 600° C. and quenched in oil. S. A. E. Steel No. 1050 after recommended heat
treatment VIII. Sorbite. Etched in 5% Nital. 500 X.
74 PHOTOMICROGRAPHS OF IRON AND STEEL
HARDENED AND DRAWN HOT-ROLLED STEEL
Fig. 95
Fig. 95. Steel. 0.85% carbon. Heated to 800° C. and quenched in oil. DrawTi
at 600° C. and quenched in oil. Sorbite. Etched in 5% Nital. 500 X.
Fig. 96. Steel. L25% carbon. Heated to 776° C. and quenched in oil. Drawn
at 600° C. and quenched in oil. Sorbite and small particles of cementite. Etched
in 5% Nital. 500 X.
STUDY OF TRANSITION CONSTITUENTS
ACCORDING TO THE METCALF TEST
Figs. 97-124 inclusive
Figs. 97-105 represent a series of photomicrographs showing the transition con-
stituents of a bar of 0.50% carbon steel heated to a very high temperature at one
end, followed by quenching the entire bar in water.
Figs. 106-112 represent a series of photomicrographs showing the transition con-
stituents of a bar of 0.85% carbon steel heated to a very high temperature at one
end, followed by quenching the entire bar in water.
Figs. 113-124 represent a series of photomicrographs showing the transition con-
stituents of a bar of 1.40% carbon steel heated to a very high temperature at one
end, followed by quenching the entire bar in water.
75
PHOTOMICROGRAPHS OF IRON AND STEEL 77
TRANSITION CONSTITUENTS — METCALF TEST
Fig. 97
Fig. 98
Fig. 97. Steel. 0.50% carbon. Microstructure of the bar after heating to atemperature exceeding; the critical range and quenching in water. Martensite andalso the persistence of austenitic grain boundaries. Etched in 5% Nital. 250 X.Original magnification, 500 X
.
Fig. 98. Steel. 0.50% carbon. Microstructure of the bar after heating to atemperature exceeding the critical range and quenching in water. Martensite.
Etched in 5% Nital. 250 X. Original magnification, 500 X.
78 PHOTOMICROGRAPHS OF IRON AND STEEL
TRANSITION CONSTITUENTS — METCALF TEST
^ ir_--*s«5. TS:
:
Fig. 99
PHOTOMICROGRAPHS OF IRON AND STEEL 79
TRANSITION CONSTITUENTS — METCALF TEST
Fig. 101
80 PHOTOMICROGRAPHS OF IRON AND STEEL
TRANSITION CONSTITUENTS — METCALF TEST
Fig. 103
Fig. 104
Fig. 103. Steel. 0.50% carbon. Microstructure of portion of the bar heated to a
temperature within the critical range and quenched in water. A series of transition
constituents, namely, martensite, troostite, troostito-sorbite, pearlite and ferrite.
Etched in 5% Nital. 250 X. Original magnification, 500 X.
Fig. 104. Steel. 0.50% carbon. Microstructureof portion of the bar heated to a
temperature within the critical range and quenched in water. A series of transition
constituents, namely, troostito-sorbite, pearlite and ferrite. Etched in 5% Nital.
250 X. Original magnification, 500 X.
I
PHOTOMICROGRAPHS OF IRON AND STEEL 81
TRANSITION CONSTITUENTS — METCALF TEST
Fig. 105
Fig. 105. Steel. 0.50% carbon. Microstructure of portion of the bar which
was heated to a temperature below the critical range and quenched in water.
A grain of pearHte, the constituents of which are arranged in a Widmanstatten or
cleavage pattern. Etched in 5% Nital. 750 X. Original magnification, 1000 X.
82 PHOTOMICROGRAPHS OF IRON AND STEEL
TRANSITION CONSTITUENTS — METCALF TEST
PHOTOMICROGRAPHS OF IRON AND STEEL 83
TRANSITION CONSTITUENTS — METCALF TEST
X
s..
Fig. 107
Fig. 107. Steel. 0.85% carbon. Microstrurtiire of a portion of the bar heated
to a temperature considerably above the critical range and quenched in water.
Austenito-martensite. Etchedin5% Nital. 375 X. Original magnification, 500X
.
84 PHOTOMICROGRAPHS OF IRON AND STEEL
TRANSITION CONSTITUENTS — METCALF TEST
Fig. 108
Fig. 108. Steel. 0.85% carbon. Microstructure of portion of the bar heated
to a temperature considerably above the critical range and quenched in water.
Austenito-martensite. The transformation of austenite to martensite took place
along the octahedral cleavage planes. Etched in 5% Nital. 375 X. Original mag-
nification, 500 X.
PHOTOMICROGRAPHS OF IRON AND STEEL 85
TRANSITION CONSTITUENTS — METCALF TEST
Fig. 109
Fig. 109. Steel. 0.85% carbon. Microstructure of portion of bar heated to
a temperature considerably above the critical range and quenched in water.
Troostito-martensite. Etched in 5% Nital. 375 X. Original magnification, 500X
.
86 PHOTOMICROGRAPHS OF IRON AND STEEL
TRANSITION CONSTITUENTS — METCALF TEST
PHOTOMICROGRAPHS OF IRON AND STEEL 87
TRANSITION CONSTITUENTS — METCALF TEST
Fig. Ill
Fig. 111. Steel. 0.85% carbon. Microstructure of portion of the bar heated to
a temperature within the critical range and quenched in water. Troostite and sorbite.
Etched in 5% Nital. 375 X. Original magnification, 500 X.
88 PHOTOMICROGRAPHS OF IRON AND STEEL
TRANSITION CONSTITUENTS — METCALF TEST
Fig. 112
Fig. 112. Steel. 0.85% carbon. Microstructure of portion of the bar heated to
a temperature within the critical range and quenched in water. Transition constitu-
ents, namely, martensite areas bounded by troostite, sorbite, and pearlite. Etched
in 5% Nital. 375 X. Original magnification, 500X.
PHOTOMICROGRAPHS OF IRON AND STEEL 89
TRANSITION CONSTITUENTS — METCALF TEST
Fig. 113 Fig. 114
Fig. 115
Fig. 113. Steel. 1.40% carbon. Microstructure of portion of the bar heated to
a temperature considerably above the critical range and quenched in water. Theoriginal twinning pattern in the austenite grain is preserved. Matrix of martensite.
Etched in 5% Nital. 250 X. Original magnification, 500 X.Fig. 114. Steel. 1.40% carbon. Microstructure of portion of the bar heated to
a temperature considerably above the critical range and quenched in water.
Troostite precipitated along the original austenite grain boundary, the matrix,
being martensite. Etched in 5% Nital. 250 X. Original magnification, 500 X.Fig. 115. Steel. 1.40% carbon. Microstructure of portion of the bar heated to
a temperature considerably above the critical range and quenched in water.
Martensite. Etched in 5% Nital. 250 X. Original magnification, 500 X.
90 PHOTOMICROGRAPHS OF IRON AND STEEL
TRANSITION CONSTITUENTS — METCALF TEST
Fig. 116
Fig. 117 Fig. 118
Fig. 116. Steel. 1.40% carbon. Microstructure of portion of the bar heated to
a temperature considerably above the critical range and quenched in water.
Troostite precipitated along the original austenite grain boundaries. Matrix of
austenite. Etched in 5% Nital. Original magnification, 500 X.
Fig. 117. Steel. 1.40% carbon. Microstructure of portion of the bar heated to
a temperature considerably above the critical range and quenched in water.
Troostite and martensite. Etched in 5% Nital. 250 X. Original magnification,
500 X.Fig. 118. Steel. 1.40% carbon. Microstructure of portion of the bar heated to
a temperature below the Acm point and quenched in water. Cementite surrounded
by troostite areas in martensite matrix. Etched in 5% Nital. 250 X. Original
magnification, 500 X.
PHOTOMICROGRAPHS OF IRON AND STEEL 91
TRANSITION CONSTITUENTS — METCALF TEST
Fig. 119
^^^y
92 PHOTOMICROGRAPHS OF IRON AND STEEL
TRANSITION CONSTITUENTS — METCALF TEST
Fig. 122
Fig. 123
^^^iM^^MMMFig. 124
Fig. 122. Steel. 1.40% carbon. Microstructure of portion of the bar heated to
a temperature below the Acm point. Cementite network, troostite and martensite.
Etched in 5% Nital. 250 X. Original magnification, 500 X.
Fig. 123. Steel. 1.40% carbon. Micrcstructure of portion of the bar heated to
a temperature within the critical range and quenched in water. Cementite network,
surrounding grains made up of martensite, troostito-sorbite and pearlite. Etched in
5% Nital. 250 X. Original magnification, 500 X.
Fig. 124. Steel. 1.40% carbon. Microstructure of portion of the bar heated to
a temperature below the critical range and quenched in water. Cementite and
pearlite. Etched in 5% Nital. 250 X. Original magnification, 500 X.
SPHEROIDIZED STEEL
Figs. 125 and 126
93
PHOTOMICROGRAPHS OF IRON AND STEEL 95
SPHEROIDIZED STEEL
Fig. 125
Fig. 125. Steel. 1.10% carbon. Partially spheroidized steel. Heated to a tem-
perature above the critical range, quenched in water, reheated 7 hours at 700° C,and cooled in furnace. Globules of cementite in matrix of ferrite with occasional
trace of pearlite. Etched in 5% Nital. 750 X. Original magnification, 1000 X.
96 PHOTOMICROGRAPHS OF IRON AND STEEL
SPHEROIDIZED STEEL
Fig. 126. Steel. 1.10% carbon. Fully spheroidized steel. Heated to a tem-
perature above the critical range, quenched in water, reheated 7 hours at 700° C,and cooled in furnace. Globules of cementite in matrix of ferrite. Etched in 5%Nital. 750 X. Original magnification, 1000X
.
GRAPHITIZED CEMENTITE
Figs. 127 and 128
97
PHOTOMICROGRAPHS OF IRON AND STEEL 99
GRAPHITIZED CEMENTITE
Fig. 127
Fig. 127. Steel. 1.10% carbon. Partially graphitized cementite. Heated 1
hour at 1000° C. and cooled in furnace. Temper carbon and pearlite. Etched in
5% Nital. 375 X . Original magnification, 500X
.
100 PHOTOMICROGRAPHS OF IRON AND STEEL
GRAPHITIZED CEMENTITE
OVERHEATED AND BURNT STEEL
Figs. 129 and 130
101
PHOTOMICROGRAPHS OF IRON AND STEEL 103
OVERHEATED AND BURNT STEEL
r^ '^ > ''v
Fig. 129
Fig. 129. Steel. 0.50% carbon. Overheated steel. Heated for 5 hours at
1100° C, and cooled in furnace. Large grains of sorbito-pearlite surrounded by a
membrane of ferrite. Etched in 5% Nital. 75 X. Original magnification, 100 X.
104 PHOTOMICROGRAPHS OF IRON AND STEEL
OVERHEATED AND BURNT STEEL
if', ' * • ', ^Afe :'.'- 'f .''.':-^y^^' //*/, •.•'V/lii^W^-.-.i'''^<^j
Fig. 130
Fig. 130. Steel. 1.25% carbon. Burnt steel. Heated to a sintering heat and
quenched in water. The grain boundaries of the metal have been badly oxidized.
Lightly etched in 5% Nital. 375 X. Original magnification, 500 X.
GRAIN GROWTH IN MILD STEEL
Figs. 131-133 inclusive
105
PHOTOMICROGRAPHS OF IRON AND STEEL 107
GRAIN GROWTH IN MILD STEEL
Fig. 131
Fig. 131. Steel. 0.08% carbon. Subjected to Brinell Ball test under a pressure
of 3000 kilograms, heated 7 hours at 650° C, and cooled slowly in furnace. Verti-
cal section through bottom of spherical depression. Etched in 12% Nital. 5.5 X.
A — Metal too severely strained to grow.
B — Junction between critically strained and unstrained metal.
C — Critically strained metal.
D — Unstrained metal.
108 PHOTOMICROGRAPHS OF IRON AND STEEL
GRAIN GROWTH IN MILD STEEL
c'-^^^^'-'^ :>^^>^..-.
ttri^- 'tr-'<
^:^< \
y^iiS^SrS#ii'i^-
J --.-^ w:i2<«t, >-^^
\r^-y:i.7 :'
Fig. 132
Fig. 132~. Steel. 0.08% carbon. Grain growth in low carbon steel. Micro-
structure at Section B shown in Fig. 131 illustrates junction between critically
strained and unstrained metal. Etched in 5% Nital. 75X. Original magnifica-
tion, 100 X.
PHOTOMICROGRAPHS OF IRON AND STEEL 109
GRAIN GROWTH IN MILD STEEL
Fig. 133
Fig. 133. Steel. 0.08% carbon. Grain growth in low carbon steel. Micro-
structure at Section C shown in Fig. 131 illustrates critically strained material.
Etched in 5% Nital. 75 X. Original magnification, 100 X.
CASE-HARDENED CARBON STEEL
AND
HEAT TREATED CASE-HARDENED CARBON STEEL
Figs. 134-142 inclusive
111
PHOTOMICROGRAPHS OF IRON AND STEEL 113
CASE-HARDENED CARBON STEEL
1
114 PHOTOMICROGRAPHS OF IRON AND STEEL
CASE-HARDENED CARBON STEEL
Fig. 136
Fig. 137
Fig. 136. Steel. 0.15% carbon. Case-hardened. Free cementite in case. Cooled
slowly from case-hardening treatment. Etched in 5% Nital. 50 X. Original magni-
fication, 100 X.
Fig. 137. Steel. 0.15% carbon. Heat treated case-hardened steel. (Same steel
as shown in Fig. 136.) Heated to 980° C, and quenched in water to refine the core.
Heated to 825° C, and quenched in water to refine the case. The presence of free
cementite in the case caused cracks to develop during the quenching operation.
Etched in 5% Nital. 50 X. Original magnification, 100 X.
PHOTOMICROGRAPHS OF IRON AND STEEL 115
CASE-HARDENED CARBON STEEL
Fig. 138
Fig. 138. Steel. Case-hardened. Example of phosphorus segregation in case of
hyper-eutectoid composition. The phosphorus rich area has not absorbed carbon
during the carburizing process. Etched in 5% Nital. 50 X. Original magnifica-
tion, 100X.
116 PHOTOMICROGRAPHS OF IRON AND STEEL
CASE-HARDENED CARBON STEEL
Fig. 139 Fig. 140
.'^^hB"lFig. 141 Fig. 142
Will give a martensitic case in hardening.
Will give soft troostitic spots in hardening.
Fig. 139. Case of normal steel.
Magnified 50 diameters.Fig. 140. Case of abnormal steel.
Magnified 50 diameters.Fig. 141. Hyper-eutectoid zone of normal steel. Magnified 200 diameters.
Fig. 142. Hyper-eutectoid zone of abnormal steel. Magnified 200 diameters.
(E. W. Ehn.) Reproduced from Sauveur's Metallography and Heat Treatment of
Iron and Steel by permission.
DECARBURIZED STEEL
Fig. 143
117
PHOTOMICROGRAPHS OF IRON AND STEEL 119
DECARBURIZED STEEL
Fig. 143
Fig. 143. Steel. 1.40% carbon. Decarburized. Heated 5 hours at a tempera-
ture considerably above the critical range and slowly cooled in furnace. The edge of
the specimen is practically carbonless. Etched in 5% Nital. 50 X. Original mag-nification, 100 X.
ALLOY STEEL
A. NICKEL STEEL
Cast, forged, annealed and after recommended heat treatment
Figs. 144-148 inclusive
121
PHOTOMICROGRAPHS OF IRON AND STEEL 123
ALLOY STEEL — NICKEL STEEL
124 PHOTOMICROGRAPHS OF IRON AND STEEL
ALLOY STEEL — NICKEL STEEL
Fig. 147
Fig. 148
Fig. 147. Nickel steel. Heat treated. 0.30% carbon; 3.50% nickel. Normal-
ized at 913° C. Heated to 902° C, and quenched in oil. Drawn at 538° C. S. A. E.
Steel No. 2330 after recommended heat treatment VII. Etched in 5% Nital.
600 X.
Fig. 148. Nickel steel. Hot-rolled. 0.30% carbon; 5.00% nickel. Etched in
6% Nital. 100 X.
B. CHROMIUM STEEL
Annealed and after recommended heat treatment
Figs. 149-154 inclusive
125
PHOTOMICROGRAPHS OF IRON AND STEEL 127
ALLOY STEEL — CHROMIUM STEEL
Ml
128 PHOTOMICROGRAPHS OF IRON AND STEEL
ALLOY STEEL — CHROMIUM STEEL
Fig. 152 Fig. 153
Fig. 154
Fig. 152. Chromium steel. Heat treated. 1.00% carbon; 1.35% chromium.
Heated to 829° C, quenched in oil. Drawn at 538° C. S. A. E. Steel No. 52100
after recommended heat treatment VI. Etched in 5% Nital. 500X.
Fig. 153. Stainless steel. Annealed. 0.30% carbon; 12.00% chromium. Etched
in Marble's reagent. 500 X.
Fig. 154. Stainless steel. Hardened and tempered. 0.30% carbon; 12.00%
chromium. Etched in Marble's reagent. 500 X.
C. NICKEL-CHROMIUM STEEL
Annealed and after recommended heat treatment
Figs. 155-158 inclusive
129
PHOTOMICROGRAPHS OF IRON AND STEEL 131
ALLOY STEEL — NICKEL-CHROMIUM STEEL
^^M
D. CHROMIUM-VANADIUM STEEL
Annealed and after recommended heat treatment
Figs. 159-162 inclusive
133
PHOTOMICROGRAPHS OF IRON AND STEEL
ALLOY STEEL — CHROME-VANADIUM STEEL
135
Fig. 159 Fig. 160
«^^J^J
E. MOLYBDENUM STEEL
Annealed and after recommended heat treatment
Figs. 163 and 164
137
PHOTOMICROGRAPHS OF IRON AND STEEL 139
ALLOY STEEL — MOLYBDENUM STEEL
Fig. 163
F. HADFIELD MANGANESE STEEL
Cast and after recommended heat treatment
Figs. 165-167 inclusive
141
PHOTOMICROGRAPHS OF IRON AND STEEL 143
ALLOY STEEL — MANGANESE STEEL
Fig. 165 Fig. 166
»'.
SILICON STEEL
(AS CAST)
Fig. 168
145
PHOTOMICROGRAPHS OF IRON AND STEEL 147
ALLOY STEEL — SILICON STEEL
Fig. 168
Fig. 168. Silicon steel. Cast. 0.15% carbon; 4.50% silicon. Typical large
grain size of high sihcon steel. Etched in 5% Nital. 50 X. Original magnifica-
tion, 100 X.
SILICO-MANGANESE STEEL
Annealed and after recommended heat treatment
Figs. 169 and 170
149
PHOTOMICROGRAPHS OF IRON AND STEEL 151
ALLOY STEEL— SILICO-MANGANESE STEEL
Fig. 169
Fig. 170
Fig.
ganese
500 X.
Fig.
ganese
169. Silico-manganese steel. Annealed. 0.50% carbon; 0.75% man-2.00% silicon. S. A. E. Steel No. 9260 annealed. Etched in 5% Nital.
170. Silico-manganese steel. Heat treated. 0.50% carbon; 0.75% man-2.00% silicon. Normalized at 927° C, reheated to 763° C, cooled slowly,
reheated to 885° C, quenched in oil. Drawn at 538° C. S. A. E. Steel No. 9260
after recommended heat treatment VIII. Etched in 5% Nital. 500 X.
CHROME-TUNGSTEN STEEL
(HIGH-SPEED STEEL)
Cast, annealed, and after recommended heat treatment
Figs. 171-177 inclusive
153
PHOTOMICROGRAPHS OF IRON AND STEEL 155
ALLOY STEEL — CHROME-TUNGSTEN STEEL
Fk;. 171 Fig. 172
Fig. 173 Fig. 174
Fig. 171. High-speed steel. Cast. 0.60% carbon; 17.00% tungsten; 3.50%chromium. Etched in 5% Nital. 250X. Original magnification, 500 X.
Fig. 172. Same spot as in Fig. 171. After repolishing and etching in Murakami'sreagent. 250 X. Original magnification, 500 X.
Fig. 173. Another spot on specimen shown in Fig. 172. After etching in Mura-kami's reagent. 250 X. Original magnification, 500 X.
Fig. 174. Another spot on specimen shown in Fig. 172. After etching in Mura-kami's reagent. 250X . Original magnification, 500 X
.
156 PHOTOMICROGRAPHS OF IRON AND STEEL
ALLOY STEEL— CHROME-TUNGSTEN STEEL
P^~<
Fig. 176
Fig. 177
Fig. 175. High-speed steel. Annealed. 0.60% carbon; 17.00% tungsten; 3.50%chromium. Carbides of chromium and tungsten in a sorbitic matrix. Etched in 5%Nital. 500 X.
Fig. 176. High-speed steel. Heat treated. 0.60% carbon; 17.00% tungsten;
3.50% chromium. Preheated in a salt bath to 926° C, then heated in a second
salt bath to 1204° C, and quenched in a third salt bath at 593° C. Carbides of
tungsten and chromium in austenitic matrix. Etched in 1% Nital and subse-
quently in Kourbatoff's reagent. 1000 X.Fig. 177. High-speed steel. Heat treated. 0.60% carbon; 17.00% tungsten;
3.50% chromium. Preheated to 816° C, heated to 1288° C, quenched in oil, and
drawn at 593° C. Etched in 1% Nital and subsequently in KourbatofiF's reagent.
1000 X.
J. SPECIAL ALLOY STEEL CONTAINING TUNGSTENAND CHROMIUM
Possessing properties of hardness after recommended heat treatment.
Seminole Steel.
Figs. 178-180 inclusive
157
PHOTOMICROGRAPHS OF IRON AND STEEL 159
ALLOY STEEL— CHROME-TUNGSTEN STEEL
Fig. 178
Fig. 178. Seminole steel as received. Containing tungsten and chromium.
Etched in 5% Nital. 500 X.
160 PHOTOMICROGRAPHS OF IRON AND STEEL
ALLOY STEEL — CHROME-TUNGSTEN STEEL
Fig. 179
Fig. 180
Fig. 179. Seminole steel. Hardened. Containing tungsten and chromium.
Etched in 5% Nital. 500 X.Fig. 180. Seminole steel. Hardened and tempered. Containing tungsten and
chromium. Etched in 5% Nital. 500 X. This steel possesses properties of hard-
ness and toughness.
K. NON-SCALING STEEL
Hadfield Era A.T.V. AUoy Steel
Fig. 181
161
PHOTOMICROGRAPHS OF IRON AND STEEL 163
ALLOY STEEL — HADFIELD ERA — A.T.V. NON-SCALING STEEL
Fig. 181
Fig. 181. Hadfield Era— A.T.V. Non-scaling steel after heating to 926° C.
and cooling in air. Etched in 5% Nital. 500 X.
CASE-HARDENED ALLOY STEEL AFTER RECOMMENDEDHEAT TREATMENT
1. Nickel steel, Fig. 182
2. Chromium steel, Fig. 183
3. Nickel-chromium steel. Fig. 184
4. Molybdenum steel, Fig. 185
5. Chrome-vanadium steel, Fig. 186
165
PHOTOMICROGRAPHS OF IRON AND STEEL 167
CASE-HARDENED ALLOY STEEL
Fig. 182
Fig. 182. Nickel steel. Case-hardened and heat treated. 0.20% carbon; 5.00%nickel. Cooled slowly in box after case-hardening and subsequently subjected todouble heat treatment. 50 X. Original magnification, 100 X.
Fig. 183. Chromium steel. Case-hardened and heat treated. 0.20% carbon;0.75% chromium. Carburized at 913° C, cooled in box. Reheated to 885° C,quenched in oil; reheated to 743° C, quenched in oil. S. A. E. Steel No. 5120 after
recommended heat treatment V. Drawn at 191° C. Etched in 5% Nital. 50 X.Original magnification, 100 X.
168 PHOTOMICROGRAPHS OF IRON AND STEEL
CASE-HARDENED ALLOY STEEL
Fig. 184 Fig. 185
Fig. 184. Nickel-chromium steel. Case-hardened and heat treated. 0.17% car-
bon; 3.50% nickel; 1.50% chromium. Carburized 7 hours at 885° C, cooled in box.
Reheated to 843° C, quenched in oil; reheated to 759° C, quenched in oil. Tem-pered at 191° C. S. A. E. Steel No. 3312 after recommended heat treatment V.
Etched in 5% Nital. 50X. Original magnification, 100 X.
Fig. 185. Molybdenum steel. Case-hardened and heat treated. 0.15% carbon;
1.50% nickel; 0.25% molybdenum. Carburized at 885° C, cooled in box. Re-
heated to 843° C, quenched in oil; reheated to 759° C, quenched in oil. Tempered
at 191° C. S. A. E. Steel No. 4615 after recommended heat treatment V. Etched
in 5% Nital. 50 X. Original magnification, 100 X.
PHOTOMICROGRAPHS OF IRON AND STEEL 169
CASE-HARDENED ALLOY STEEL
y/7^
Fig. 186
Fig. 186. Chrome-vanadium steel. Case-hardened and heat treated. 0.20%carbon; 0.95% chromium; 0.18% vanadium. Carburized at 913° C, cooled in box.
Reheated to 885° C, quenched in oil; reheated to 742° C, quenched in oil. Tem-pered at 191° C. S. A. E. Steel No. 6120 after recommended heat treatment V.
Etched in 5% Nital. 50 X. Original magnification, 100 X.
ANNEALED NITRALLOY
(STEEL USED FOR NITRIDING)
AND
NITRIDED STEELS
Figs. 187-193 inclusive
171
PHOTOMICROGRAPHS OF IRON AND STEEL 173
NITRALLOY AND NITRIDED NITRALLOY
Fig. 187
Fig. 18S
Fig. 187. Nitralloy. Annealed. 0.36% carbon; 0.51% manganese; 0.27% sili-
con; 1.23% aluminum; 1.49% chromium; 0.010% sulphur; 0.013% phosphorus;
0.18% molybdenum. Etched in 5% Nital. 500 X.
Fig. 188. Nitralloy after subjected to nitriding process. Etched in 5% Nital.
50 X. Original magnification, 100 X.
174 PHOTOMICROGRAPHS OF IRON AND STEEL
NITRIDED NITRALLOY
Fig. 189
Fig. 190 Fig. 191
Fig. 189. Microstructureof section J.. Shown in Fig. 188. Etchedin 5% Nital.
250 X. Original magnification, 500 X.
Fig. 190. Microstructure of section B. Shown in Fig. 188. Etched in 5% Nital.
250 X. Original magnification, 500 X.
Fig. 191. Microstructure of section C. Shown in Fig. 188. Etched in 5% Nital.
250 X. Original magnification, 500 X.
PHOTOMICROGRAPHS OF IRON AND STEEL 175
NITRIDED NITRALLOY
Fig. 192
Fig. 193
Fig. 192. Microstructure of section D. Shown in Fig. 188. Etched in 5% Nital.
500 X.
Fig. 193. Microstructure of section E. Shown in Fig. 188. Metal unaffected
by nitriding. Etched in 5% Nital. 500 X.
f
CAST IRON
(GRAY IRON)
Figs. 194-201 inclusive
177
PHOTOMICROGRAPHS OF IRON AND STEEL ]79
GRAY CAST IRON
Fig. 194 Fig. 195
Fig. 190 Fig. 197
Fig. 194. Gray cast iron. No combined carbon. Graphite and ferrite. Etchedin 5% Nital. 250 X. Original magnification, 500 X.
Fig. 195. Gray ca.st iron. No combined carbon. Graphite, ferrite and steadite.
Etched in 5% Nital. 250 X. Original magnification, 500 X.Fig. 196. Gray cast iron. Hypo-eutectoid matrix, containing about 0.40% com-
bined carbon. Graphite, pearlite, ferrite and steadite.
Fig. 197. Gray cast iron. Hypo-eutectoid matrix, containing about 0.60% com-bined carbon. Graphite, pearlite and ferrite. 250 X. Original magnification,
500X.
180 PHOTOMICROGRAPHS OF IRON AND STEEL
GRAY CAST IRON
Fig. 198 Fig. 199
Fig. 200 Fig. 201
Fig. 198. Gray cast iron. Hypo-eutectoid matrix, containing about 0.60% com-
bined carbon. Graphite, pearlite, steadite and ferrite. Etchedin5% Nital. 250 X.
Original magnification, 500 X.
Fig. 199. Gray cast iron. Eutectoid matrix, containing about 0.85% combined
carbon. Graphite and pearUte. Etched in 5% Nital. 250 X. Original magnifica-
tion, 500 X.
Fig. 200. Gray cast iron. Eutectoid matrix, containing about 0.85% combined
carbon. Graphite, pearlite and steadite. Etched in 5% Nital. 250 X. Original
magnification, 500 X.
Fig. 201. Gray cast iron. Hyper-eutectoid matrix, containing about 1.25%
combined carbon. Graphite, sorbite and cementite. Etched in 5% Nital. 250 X.
Original magnification, 500 X.
MOTTLED CAST IRON
Fig. 202
181
PHOTOMICROGRAPHS OF IRON AND STEEL 183
MOTTLED CAST IRON
Fig. 202
Fig. 202. Mottled cast iron. Cementite, pearlite and graphite. Etched in 5%Nital. 250 X. Original magnification, 500 X.
WHITE CAST IRON
Figs. 203 and 204
185
PHOTOMICROGRAPHS OF IRON AND STEEL 187
WHITE CAST IRON
^K5ib*!
Fig. 203
Fig. 203. White cast iron. Cementite and pearlite. Etched in 5% Nital.
375 X. Original magnification, 500 X-
188 PHOTOMICROGRAPHS OF IRON AND STEEL
WHITE CAST IRON
Fig. 204
Fig. 204. White cast iron. Cementite and pearlite. Etched in 5% Nital.
375 X. Original magnification, 500X.
MALLEABLIZED CAST IRON
Figs. 205 and 206
189
PHOTOMICROGRAPHS OF IRON AND STEEL 191
PARTIALLY MALLEABLIZED CAST IRON
Fig. 205
Fig. 205. Cast iron. Partially malleablized. Ferrite, temper-carbon and sorbito-
pearlite. Etched in 5% Nital. 375 X. Original magnification, 500X
.
192 PHOTOMICROGRAPHS OF IRON AND STEEL
FULLY MALLEABLIZED CAST IRON
Fig. 206
Fig. 206. Cast iron. Fully malleablized. Ferrite and temper-carbon. Etchedin 5% Nital. 375 X. Original magnification, 500 X.
MANGANESE SULPHIDE IN CAST IRON
Fig. 207
193
PHOTOMICROGRAPHS OF IRON AND STEEL 195
MANGANESE SULPHIDE IN MALLEABLIZED CAST IRON
Fig. 207
Fig. 207. Manganese Sulphide in partially malleablized cast iron. Rounded
particles of dove-gray manganese sulphide in ferrite. Temper-carbon and sorbito-
pearlite present. Etched in 5% Nital. 500X.
PHOSPHIDE EUTECTIC IN CAST IRON
Figs. 208-210 inclusive
197
PHOTOMICROGRAPHS OF IRON AND STEEL 199
PHOSPHIDE EUTECTIC
Fig. 208
^ir'grg ^W> .-N- '
t.v. j^ '
^^" ; ' \ifl^^t ^
Fig. 209
Fig. 208. Phosphide eutectic after etching in 5% Nital. 250 X. Original mag-
nification, 500 X.
Fig. 209. Same as in Fig. 208, after repolishing and etching in sodium picrate.
250 X. Original magnification, 500 X.
200 PHOTOMICROGRAPHS OF IRON AND STEEL
PHOSPHIDE EUTECTIC
Fig. 210
Fig. 210. Same spot as shown in Fig. 209, after repolishing and heat-tinting.*
The dark-colored plates in the print represent a deep lavender color, — phos-
phorus rich areas. The bright-colored plates in the eutectic represent a j^ellow-
ish-red color — cementite areas. 250 X. Original magnification, 500 X.
* The polished specimen was placed on a hot plate and heated by a Bunsen gas burner until the
phosphorus rich areas were tinted a deep lavender.
CHILLED CAST IRON
Showing a series of Photomicrographs of a chilled casting
Figs. 211-213 inclusive
201
PHOTOMICROGRAPHS OF IRON AND STEEL 203
CHILLED CAST IRON
Fig. 211 Fig. 212
Fig. 213
Fig. 211. Microstriicture of chilled face of gray iron casting. Etched in 5%Nital. 250 X. Original magnification, 500 X.
Fig. 212. Microstructure of junction of chill and gray iron. Etched in 5%Nital. 250 X. Original magnification, 500 X.
Fig. 213. Microstructure of gray iron. Etched in 5% Nital. 250x. Original
magnification, 500 X.
SEMI-STEEL
Comparative microstructures of gray cast iron with
a eutectoid matrix, Fig. 214, and a semi-steel
with a eutectoid matrix, Fig. 215
205
PHOTOMICROGRAPHS OF IRON AND STEEL 207
SEMI-STEEL
^n^
CAST IRON CONTAINING SPECIAL ELEMENTS
Figs. 216-218 inclusive
209
PHOTOMICROGRAPHS OF IRON AND STEEL 211
SPECIAL ELEMENTS IN GRAY CAST IRON
Fig. 216
Fig. 217
Fig. 216. Gray cast iron. Hypo-eutectoid matrix. 3.16% total carbon; 2.63%silicon. Etched in 5% Nital. lOOX.
Fig. 217. Nickel. Gray cast iron. Hypo-eutectoid matrix. 3.17% total car-
bon; 1.14% silicon; 2.83% nickel. Etched in 5% Nital. lOOX.
212 PHOTOMICROGRAPHS OF IRON AND STEEL
SPECIAL ELEMENTS IN GRAY CAST IRON
Fig. 218
Fig. 218. Nickel-Chromium. Gray cast iron. Hypo-eutectoid matrix. 3.11%
total carbon; 2.20% silicon; 1.11% nickel, and 0.38% chromium. Etched in 5%Nital. 100 X.
APPENDICES
APPENDIX ATHE PREPARATION OF METALLOGRAPHIC
SPECIMENS*
By H. M. Boylston, Professor of Metallurgy, Case School of Applied Science,
Cleveland, Ohio.
Selection of Specimen. — Metallographic specimens should be so selected
as to be representative of the metal from which they are taken. Where the
piece has failed in service it is important that a specimen should be taken
from near the failure and one considerably distant from it for comparison or
samples may sometimes be obtained from similar pieces which have stood up
well in service.
When samples are taken from near a fracture, the metal very close to the
fracture itself should be examined. The fracture edge should not be bevelled
and sometimes it is well to electroplate the fractured surface with copper
(Rosenhain), in order to protect the fracture from bevelling during subsequent
grinding and polishing operations. Embedding the plated specimen in fusible
metal, as explained below, is sometimes advisable.
Note should be made of the location of the specimen in the piece and the
relation of the surface to be polished to the direction of forging and rolling.
A sketch is very helpful in this connection.
Removal of Specimen. — Specimens are generally cut off with a hack saw.
Tough steels, like manganese steel and other austenitic material, hardened
steels, or even white cast iron, wliich cannot be cut with a hack saw, may be
cut easily with a thin alundum or carborundum disc, three-thirty-seconds
of an inch thick and running in water, if it is necessary to prevent tempering.
If no cutting disc is available brittle specimens may be broken with a hammer,
although this means a rough surface to grind down later.
Dimensions of Specimen. — Much time is saved by keeping the specimen
small within reasonable lunits. A one-half inch square or round piece is a
good size unless the microscope is of such construction that a larger piece is
necessary in order to prevent it from slipping through the stage. It is mucheasier and quicker to polish four pieces each one-half inch square than it is
to polish one piece one inch square. The thickness of the specimen should
be less than the other dimensions, if possible, since the thicker the specimen
the more difficult it is to hold it on the grinding and polishing wheels without
rounding the surface. A one-half inch square or round piece should be prefer-
ably not over three-eighths inch thick. Very small specimens may be embedded
* Printed from the American Society for Steel Treating handbook, by permission.
215
216 APPENDIX A
in some fusible metal, sealing wax, fiber or by mounting in suitable metal
clamps. (See Figs. 1, 2, and 3.) By these means the finest wire, turnings and
even filings may be polished and examined. The following alloy, suggested
by Champion and Ferguson, which melts in boiling water, is very useful in
mounting small specimens:
Bismuth 50 parts by weight
Lead 30 parts by weight
Tin 25 parts by weight
Zinc 3 parts by weight
^
APPENDIX A 217
paper gives good results. Some grind on a coarse file, but this is preferably-
restricted to soft metals. Grinding wheels may be mounted either vertically
or horizontally and should be run at a speed of about 1200 R.P.M. The
specimen should be kept cool on the grinding wheel by having water drip on it.
Light pressure should be maintained on the specimen on all wheels or papers,
whether for grinding or polishing. The edges of the specimen should be bev-
elled where possible, in order to protect the cloth or paper from being cut.
Specimens should be washed thoroughly in water after the grinding operation,
in order to remove any trace of abrasives. There are two reasons for grinding
specimens: first, to remove the marks of the saw or cutting disc, and in order
to know when this has been accomplished it is wise to hold the specimen so
that the grinding marks are at right angles to those already found on the surface
to be prepared. The second reason for grinding is to have an absolutely flat
surface.
Rough Polishing. — This may be done with grade FF Turkish flour emery
powder or French emery paper No. 1. The powder should be suspended in
water and used on a smooth wheel of some sort covered with 12 ounce canvas
duck. Very little powder and much water should be used, and again the speci-
men should be turned 90 degrees so that the scratches produced by the powders
or papers will be at right angles to those produced in grinding. The specimen
should be washed thoroughly in water before passing to the next step, to remove
all traces of abrasives. Some prefer to supplement the rough polish with
French emery paper 0, 00 and 000.
Fine Polishing. — Two or more steps are generally used. In the first step
white reground tripoli powder or alundum powder No. 600 may be used in
water suspension and placed on a wheel covered with a fine grade of broadcloth.
The cloth should not be too thick or a relief polish will be obtained. Plenty
of water and not too much powder should be used.
The last operation may be performed with fine levigated alumina, grade
No. 3, or with "superfine" magnesia powder. The best soft, high grade,
jewelers' rouge powder may also be used. Levigated alumina or magnesia
generally give better results than rouge, which is apt to scratch soft specimens.
For this final operation "kitten's ear" silk broadcloth is preferable. Whenlevigated alumina is used it should be suspended in water and squirted on the
cloth disc by means of a devilbiss atomizer or any other type having a broad
orifice. If magnesia is used it will harden and cake slightly unless the cloth
is removed each time and kept soaked in a weak solution (2 per cent) of hydro-
chloric acid (HCl) in distilled water. An exceptionally small amount of
powder is necessary in the final polishing operation.
Except where otherwise indicated, all suspended powders may be placed on
the cloth covered disc by means of rubber set varnish brushes. Some prefer
to wash off the powder from the cloth in the final polishing and polish for a
few moments on the cloth alone, which is thoroughly wet with water.
While the speed for grinding has been given as 1200 R.P.M. it is better to
use lower speeds in the three other operations; namely, 300 to 600 R.P.M.
218 APPENDIX A
In every case specimens should be washed thoroughly after each stage of
the operation.
Especially soft metals, like lead alloys, must be ground and polished byhand throughout the entire operation. In grinding the soft specimens the
specimens should be rubbed over the file and not have the file passed over them.
Washing and Drying. — Specimens should be thoroughly washed in water
after polishing and then washed in two baths of absolute alcohol and dried
immediately by means of a blower. The best instrument for diying is some
form of barbers' hair dry^er. Specimens should not be touched with the fingers
after washing and drying or a greasy surface will be produced which will not
etch evenly. Specimens should be carefully wrapped in cotton or placed in a
desiccator until ready to etch and in the case of copper alloys etching and
photography should be carried out as promptly as possible to avoid troubles
due to tarnish.
Refeeences
Sauveur's Metallography and Heat Treatment of Iron and Steel, third
edition, 1926.
Guillet and Portevin Metallography and Macrography, second edition, 1922,
Chapter 1.
Goerens and Ibbotson, Introduction to Metallography, 1908, pages 121 to 130.
C. H. Desch, third edition, 1922, Chapter VII.
S. L. Hoyt, Metallography — Principles, 1920.
W. Rosenhain, Introduction to the Study of Physical Metallurgy, 1914.
C. 0. Burgess and J. R. Vilella, "Transactions," A. S. S. T., vol. 7, page 486,
1925.
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220 APPENDIX B
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222 APPENDIX B
APPENDIX B 223
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228 APPENDIX B
References
Sauveur, "Metallography and Heat Treatment of Iron and Steel," 1926.
Hoyt, "Metallography," 1920.
Goerens and Ibbotson, "Introduction to Metallography," 1908.
Guillet and Portevin Taverner, "Metallography and Macrography," 1922,
"Pamphlet No. 403," U. S. Bureau of Ordnance, Oct. 1916.
"Circular No. 113," Bureau of Standards, 1922.
Kerns, "Foundry Data Sheets," June 1 and 15, 1920.
Groesbeck, Metallographic Etching Reagents, "Scientific paper No. 518,"
Bureau of Standards, 1925.
Hudson, Etching Reagents and Their Application, "Journal," Institute of
Metals, Vol. 13, page 193, 1915.
Pilling, Microscopic Detection of Carbides in Ferrous Alloys, "Transactions,"
A. I. M. E., Vol. 70, page 254, 1924.
Sauveur and Krivobok, Use of Sodium Picrate in Revealing Dendritic Segre-
gation in Iron Alloys, "Transactions," A. I. M. E., Vol. 70, page 239, 1924.
Vilella, Delving into Metal Structures, "Iron Age," Vol. 117, page 761, 1926.
I
APPENDIX C
MICROSCOPES
By W. L. Patterson*
The use of the Microscope in Metallurgy differs somewhat from ordinary-
uses in that the objects are opaque and must be illuminated from above gen-
erally by means of a vertical illuminator.
Any ordinary microscope may be used if proper objectives are available (see
objectives). As the metal specimens vary in thickness they must either be
mounted at a uniform height or the illuminating device must be attached to
the vertical illuminator to move with it when focusing.
The usual table or students microscope used for the examination of metal
has an adjustable stage to provide for differences in thickness.
In both of the forms described the specimens must be mounted with the
polished side up and levelled so that the face of the specimen is perpendicular
to the optical axis of the microscope.
Where many specimens are to be examined and highest powers used as in
research the inverted form of microscope is to be preferred. In this form the
stage is above the optical parts and the specimen is placed upon the stage
with the polished side down.
Objectives
The objectives (the lens nearest the specimen) are especially made for this
work by being corrected for use without coverglass. This difference is scarcely
noticeable on power of sixteen millimeter or less in focus but in the higher powers
the definition is poor unless properly corrected objectives are used.,
Objectives are made in a variety of focal lengths such as 48, 32, 16, 8, 4 and 2
millimeters and their initial magnifying powers are 2, 4, 10, 20, 43 and 100
respectively. By initial power is meant that the objective alone gives an
image of certain magnification which in turn is again magnified by the eyepiece.
We thus have the compound microscope. These initial magnifications vary
in accordance with the distance between the eyepiece and the objective the
greater the distance the greater the magnification.
While this might seem a ready means of increasing or decreasing the mag-nification it does not prove successful in practice as the lenses are mathematically
calculated to produce the best images at a particular distance. This distance
is known as tube length and varies with different makers and on different types
* Mr. Patterson of the Bausch and Lamb Optical Company, Rochester, NewYork, very kindly wrote this article at the author's request.
229
230 APPENDIX C
of microscopes. The objectives are usually engraved with the tube length
for which they are corrected and this distance is found by measuring the length
of the tube from the shoulder against which the objectives screws to the shoulder
against which the eyepiece rests.
The resulting magnification is the product of the objective power and the
eyepiece power. (See eyepieces.)
These magnifications are based on the observation of a vertical image appear-
ing at a distance of 250 millimeters in front of the eye, when looking into the
microscope. They may be checked by projecting a real image at 250 mm.from the eyepiece.
Eyepieces
The eyepiece (lens nearest the eye) is used to magnify the image formed bythe objective. Eyepieces are made in focal lengths of 50, 40, 33, 25, 20, 16 mm.with magnifications of 5, 6.4, 7.5, 16, 12.5 and 15 respectively. As stated
under objectives it is the power of the objective multiplied by the power of
the eyepiece, at correct tube length, which gives the total power of the micro-
scope. Thus a 16 mm. focus objective of lOX with an eyepiece of 25 mm.focus of lOX gives at 160 mm. tube length a magnification of 100 diameters.
Vertical Illuminators
Vertical illuminators in common use are of two forms, the plane glass which
covers the entire aperture of the objective and reflects light down through the
objective to the specimen and at the same time permits the light to pass through
it to the eyepiece and eye. This gives true central illumination and is preferred
by many.
The second form consists of a mirror or prism covering part of the objective
aperture the light going to the specimen through one side of the objective and
returning on the opposite side. This gives an angular illuinination and is
useful in bringing out in relief parts of the specimen wliich may be above or
below the principal surface.
Illuminants
lUuminants for metal examinations are usually the incandescent lamp or
the arc lamp. The former is nearly always used in table work and may be
used in photography although due to its less intensity longer exposures are
required than with the arc. Only incandescent lamps with very compact
filament should be used if good results are to be obtained. The ribbon form
of filament is the best, other concentrated forms may be used but as the illumi-
nant is usually focused upon the specimen the scattered filament gives an
uneven illuinination.
The arc lamp consists of two carbons automatically fed together as they
consume and the light is taken from the crater of the upper carbon. Direct
current should always be used with the arc lamp if available and if not available
it is probably best to use the incandescent lamp.
APPENDIX C 231
Cameras
Any camera can be used to make a picture with the microscope but due to
the necessity of soHdity, proper centering, etc., it is best to use a camera espe-
cially made for photo-niicrographic work.
The ultimate goal of every metallographer should be toward a complete
outfit meeting all the requirements for the finest work. The illustration shows
one of this type where all parts are built for this particular work. See Fig. 4.
^^^^^^^^P
APPENDIX DPHOTOMICROGRAPHY*
By Walter M. MixcHELLf and H. M. BoylstonJ
The photomicrography of poHshed and etched specimens of metals with the
aid of a microscope is important as a means of securing records of their micro-
structure for reference and future examination. The production of such photo-
graphs, called photomicrogra])hs (not microphotographs, which are merely
photographs of microscopic size), requires proper care and skill in the manipu-
lations, if satisfactory results are to be obtained. Before photomicrographic
work is attempted, four things are essential:
(a) The microscope and the source of illumination must be in proper adjust-
ment, individually and with each other.
(6) The microscope must be so mounted that it will be free from vibration.
Ordinary vibrations are harmless if all parts of the apparatus are tightl}^ clamped
together.
Vibrations from steam hammers and from railroad trains passing close to
the laboratory can be minimized by placing several inches of sponge rubber
under the legs of the stand. If this does not correct the trouble the outfit
may be suspended from the ceiling with spiral springs, or a spring suspen.sion
stand may be used.
(c) Specimens must be polished flat and free from scratches.
(d) If the specimen is etched, the structure should be as clean cut as pos.sible.
Lighter etching than that used in low power work is necessary for good results
at high magnifications.
Magnifications. — It is recommended that the following standard magnifica-
tions be used in making photomicrographs (expressed in diameters): for
ferrous materials, 10, 50, 100, 250, 500, 1000, 2000, 5000; for non-ferrous
materials, 10, 25, 50, 75, 100, 150, 200, 250.
The term photomacrograph is generally applied when the magnification is
less than 10 diameters. In photomacrography the following magnifications
are commonly used (expressed in diameters): |, 1, li, 2, 2?, 3, 5.
Generally speaking, it is better to use a higher power objective rather than
a lower for obtaining a given magnification if maximum resolution is desired,
but too short a bellows length (projection distance) is also to be avoided.
* Printed from the American Society for Steel Treating handbook, by permission.
t Dr. Walter M. Mitchell is metallurgist. Central Alloy Steel Corp., Canton, Ohio,
t H. M. Boylston is professor of metallurgy, Case School of Applied Science,
Cleveland, Ohio.
232
APPENDIX D 233
Lenses. — In the following table are given the various lenses and lens com-
binations which are convenient for obtaining different magnifications.
Lenses for Various Magnifications
234 APPENDIX D
where M is the magnification to be determined, D the projection distance
measured in miUimeters, and M' the magnification of a particular combination
of eyepiece and objective at 250 mm. (10 inches) projection distance. Thevalues of M' are generally supplied by the manufacturer in a table accompanying
the microscope, and may be given as the magnification at the eye, since the
lens of the eye produces on the retina an image with a magnification corre-
sponding to that obtained in projection at a distance of 250 mm. from the outer
focus of the eyepiece. Since this outer focus of the eyepiece is very close (about
3 mm. away) to the lens of the eyepiece the projection distance may be measured
roughly by determining the distance from the eyepiece lens to the near side
of the focusing screen.
Illumination of Specimens, — For use with objectives of 32 mm. focal
length or less, all of which are used in combination with oculars, vertical illu-
mination (i.e., normal to the surface under observation) is usually necessarv.
Either the plane-glass or mirror type of illuminator (the latter including the
totally reflecting prism) in which the reflector is placed between the objective
and the ocular may be used. For the best results, the condition of "critical
illumination" should be obtained; that is, the optical distance from the source
of light (real or apparent) to the surface of the specimen should equal the
distance from the specimen to the focal plane of the ocular, or, in other words,
the source of light should be approximately imaged on the specimen. Themirror or prism type of illuminator is not suitable for very short focus objec-
tives (4 mm. or less), since it obscures a relatively large portion of the lens
aperture.
With objectives of the photographic type, vertical illumination is obtained
by inserting the illuminator (plane-glass) between the lens and the surface of
the specimen. Oblique illumination may be obtained by directing a beam of
light so that it strikes the surface of the specimen obliquelj^ or, in a lesser degree,
by rotating the reflector of the vertical illuminator. A special form of oblique
illumination known as "conical illumination" and methods for obtaining it
are described by H. S. George in the Transactions, A. S. S. T., Vol. IV, 1923,
page 140.
For lenses of the photographic type of more than 48 mm. focal length the
illumination should be difl'used, for example, daylight, or oblique, as obtained
by directing a beam of light upon the specimen obliquely from one side; or
vertical, by means of a large plane-glass placed between the lens and the object.
In order to increase the size of the field, which otherwise would be restricted
in diameter to that of the photographic lens, a relatively large plano-convex
lens should be placed between the reflecting plane-glass and the source of light,
the lens being located so that the optical distance between it and the photo-
graphic lens equals the focal length of the plano-convex lens. Moistening the
surface of the specimen with water, glycerin or oil, or even immersing the entire
specimen in alcohol or water, will often be found desirable for the purpose of
increasing the contrast in the photograph.
In the case of fractured specimens, a good reproduction of the fractured
APPENDIX D 235
surface may be readily obtained by using two sources of artificial light of unequal
intensities. Place one source of light on each side of the specimen. A reflector
may be used in place of the weaker light source if desired. The second, or
weaker, illuminant serves to neutralize partially the deep shadows cast by the
stronger one and so produces a good relief effect.
Photographic Plates. — The most convenient size of plate or film for the
average laboratory is 4 X 5 inch, but economy may be effected where a great
many negatives are made daily by using a size 3i X 4i in h. Occasionally
a 5 X 7 inch negative or even an 8 X 10 inch negative will be advantageous,
especially in macrographic work.
Various types of plates are listed below because of the difficulty in some
localities of obtaining some preferable types. It is simpler and easier, however,
to learn how to use one plate or film to the best advantage and stick to it.
The Wratten M (panchromatic) plates have a special fine grained emulsion
which gives a veiy desirable combination of detail and contrast. This detail
and contrast may be varied according to requirements by the use of monochro-
matic color screens. The Wratten filters, or screens, are as follows: B (green),
F (red), K (yellow), etc. Nothing is gained by using these plates unless a
monochromatic screen is used in conjunction with them.
\\Tiile it is necessary, for the best results, to handle and develop Wratten Mplates in complete darkness, the makers include in each box of plates a card
giving the proper time of development for that particular emulsion. Allowance
is made for low contrast, normal contrast, great contrast and varying tem-
peratures of developer; thus an opportunity is afforded for the exercise of
judgment on the part of the operator depending upon the conditions surround-
ing the making of the negatives. There are other panchromatic plates but
they do not give as good results.
One of the disadvantages of panchromatic plates is their poor keeping quali-
ties, especially in warm weather.
The following brands of orthochromatic (isochromatic, i.e., sensitive to yellow
light) plates may be used in conjunction with yellow or green screens with
complete satisfaction, but they cannot be used with a red filter:
Medium Speed: Standard Orthonon; Cramer Medium Iso; Stanley;
Hammer Special Nonhalation Ortho.
Slow Speed: Cramer Slow Iso; Hammer Slow Ortho.
These plates are of average contrast, fine grained, and may be used for
structures which show considerable contrast.
Plates giving greater contrast but requiring slightly longer exposure are:
Medium and Slow Speed: Cramer Commercial Isonon; Stanley Commer-cial; Hammer Commercial Ortho.
Photographic Films. — The use of films for photomicrographic work has
much to commend it. The cut films are easily handled in frames which hold
them flat in the ordinary plate holder. Other frames of special non-corrodible
material are available for holding the films in the developer tank and fixing
box. Films do not crack or break during storage or shipment and take up
236 APPENDIX D
less space. They apparently stay flat during exposure since the negatives do
not show "out of focus" areas. They are not yet available in the Wratten Memulsion but can be had in the Standard Orthonon type, and should be used
in conjunction with a Wratten B or a K filter for the best results.
Monochromatic Filters. — Since all photographic plates are most sensitive
to blue light, for which the objective lenses are not corrected, and since the
yellowish green rays are those most easily distinguished at the focusing screen,
it is necessary to absorb the blue rays with a suitable color screen or filter.
Through their use a good achromatic lens gives just as good or better results
as an expensive apochromat. Moreover, apochromatic lenses always have a
residual spherical aberration resulting in lack of flatness of field in spite of
so-called compensating eyepieces. Most American achromats are corrected
for the very color obtainable with a Wratten B (green) filter, so the latter is
obviously the correct one to use in conjunction with a plate which is sensitive
to green light, such as the Wratten M or the Standard Orthonon, Cramer Iso
or Hammer Special Nonhalation Ortho. Some prefer a Wratten Ki, Ko or Ksfilter, while others prefer the Wratten M plates and the Wratten B (green)
screen. If the exposure is correct (and there is considerable latitude allowed)
and the development correct, any gradation of detail and contrast may be
obtained with this combination at low, medium or high magnification. Thegreen color is also the most restful to the eye in visual work especially if a white
ground screen is used in combination with it.
Red screens (Wratten F) give more contrast and somewhat less detail than
green (Wratten B) and are preferable in macrography where minute detail
is less important than maximum contrast.
Theoretically, it would seem as if a blue filter (short wave length) in con-
junction with a proper plate would give better results where fine details are
to be photographed at high magnification, but this does not appear to be borne
out in the experiences of many of the most careful workers. Light of short
wave length may have its advantages in the case of stained transparent objects
using transmitted light, but it appears to offer no special advantage in metal-
lography.
For the best results the filter used should be kept in place while adjusting the
final focus at the focusing screen.
Some workers use a liquid filter such as a nickel chloride solution for green,
or one of the green Aniline dyes, and for a yellow filter a saturated solution of
potassium bichromate, but it is difficult to keep the solutions free from air
bubbles and at the proper strength because of evaporation. A well madeglass filter will last indefinitely if maintained at a point in the beam of light
where the heat from the light is at a minimum.
Exposure of Negative. — The time of exposure varies with the following
factors
:
(a) Character of Specimen. — Bright or light colored structures, such as free
ferrite or free cementite, require shorter exposures than dark ones like troostite,
sorbite, pearlite, etc., and generally speaking, the darker the general appear-
APPENDIX D 237
ance of the structure and the less contrast it contains the longer will be the
proper time of exposure.
(b) Speed of Plate. — The faster the plate, the shorter will be the exposure
required.
(c) lutensitij of Light. — With a good carbon arc light and with iris dia-
phragms and settings of the optical system arranged to give critical illumina-
tion, the exposure required at 100 diameters magnification usmg direct current,
a Wratten M plate and a Wratten B filter is approximately eight seconds.
With alternating current under the same conditions the required exposure is
twelve seconds. With a tungsten arc light which can be used only with direct
current, and other conditions as stated, the required exposure is about forty-five
seconds. With a 6 volt, 24 watt, automobile headlight type of Mazda incan-
descent lamp the corresponding exposure would be about si.xty seconds.
(d) Color of Light. — If the proper exposure with carbon arc and green
(Wratten B) filter at 100 diameters is eight seconds, the exposure under similar
conditions with a red (Wratten F) filter would be approximately six seconds
for a Wratten M plate. For a yellow filter (K2) and other conditions the same
as stated the exposure would be approximately four seconds.
(e) Magnification Used. — If the exposure required at 100 diameters is eight
seconds the exposure recjuired at 400 diameters would be approximately forty
seconds or at 1000 diameters it would be approximately sixty seconds.
(/) Size of Opening in Iris Diaphragms. — The size of the opening in the
iris diaphragm between the source of light and the first condenser in most
American instruments controls, to a considerable degree, the resolution of
detail in the image; the smaller the opening the greater the resolution, but
it is also true that the smaller the opening the longer the exposure.
If the correct exposure time has not been obtained from the information
given above then this should be determined by experience and trial. Adopt
a system of making all exposures at standard magnifications of, say, 50X,
lOOX, 500X, lOOOX, 2000X, 5000X. If this is done, after a little experience,
the proper exposure time can be estimated by the appearance of the image
on the focusing screen. The correct exposure time may be easily determined
by exposing successive portions of a test plate to progressively longer exposures.
Draw slide out of the plateholder so as to expose one inch of the plate, expose
for 5 seconds, draw the slide out another inch, expose again for 5 seconds, and
repeat until the whole plate is exposed. On developing, that strip which is
correctly developed will indicate the proper exposure time. In any case the
exposure should be sufficiently long so that the darker portions of the structure
will be fully exposed; otherwise no details in these will be recorded and they
will appear dead black in the final print.
Plate Developers. — The safest and most convenient developer is generally
that recommended by the plate or film manufacturer who is in a position to
know what developer is best suited to the particular emulsion furnished. Direc-
tions are generally given on a card or pamphlet found inside the box of plates
or films.
238 APPENDIX D
The developer recommended by the manufacturer of Wratten M plates is
as follows:
Pyro Soda DEVELOPf:R
Developing Formula for Wratten and Wainwright M Plates
Do not wet the film before applying developer
Avoirdupois Metric
A. Potassium Metabisulphite 250 grains 17 grams
Sodium Sulphite (desiccated) 2| ozs. 70 gramsPyrogallic Acid f oz. 20 gramsWater to 32 ozs. 1000 cc.
Dissolve in order given.
B. Sodium Carbonate (desiccated) 2f ozs. 75 grams
Potassium Bromide 15 grains 1 gramWater to 32 ozs. 1000 cc.
Use equal parts of "A" and "B."
Typical Time of Development with above Formula in Minutes.
Time varies somewhat with different batches of plates.
Temperature
APPENDIX D 239
Dissolve Elon before adding sodium sulphite; otherwise it may be reprecipi-
tated: add other ingredients in order given.
For a working strength developer, use equal parts of A, of B, and of water.
Contrast Plate Developer
Avoirdupois Metric
A. Water (distilled) 32 ozs. 1000 cc.
Sodium sulphite (desiccated) 2f ozs. 80 gramsHydrochinone -. § oz. 15 gramsPotassium bromide i oz. 8 grams
B. Water (distilled) 32 ozs. 1000 cc.
Caustic potash If ozs. 48 grams
For a working strength developer, use equal parts of A, of B, and of water.
Ordinary' tap water may be used if free from iron salts.
The stock solution will keep indefinitely if stored in well filled, tightly corked
bottles.
Either of the above developers in mixed solution inay be used until exhausted,
5 ounces of the mixed solution being sufficient for one-half dozen 4x5 inch
plates or their equivalent. Developer should be used at a temperature of
65 degrees Fahr. This is very important, since higher temperatures will give
failure due to "frilling" of the emulsion. At 65 degrees Fahr. development
of a properly exposed plate will be complete in 3 to 5 minutes; longer time will
increase the density of the negative, necessitating longer printing time, and
increase the contrast. Insufficient development under above conditions indi-
cates underexposure.
After the plates are developed they should be rinsed thoroughly in water
and fixed in the following fixing bath:
Chrome Alum Fixing Bath
Avoirdupois Metric
Water 32 ozs. 1000 cc.
Hypo 12 ozs. 350 grams
When dissolved, add 1| ozs. (50 cc.) of the following hardening solution:
Water 3^ ozs. 100 cc.
Chrome alum 185 grains 12 gramsSodium bisulphite 308 grains 20 grams
This bath ceases to harden the gelatine film after keeping for several days,
so that in warm weather if the film tends to soften a fresh fixing bath should
be prepared daily.
In cold weather use one-half the quantity of hardening solution. If precipita-
tion of dirty white and finely divided sulphur occurs, as sometimes happens
while mixing or on long standing, it is better to throw the bath away and pre-
pare a new one. Do not use old or discolored fixing baths.
The following fixing bath, although it will not harden the gelatine film as
240 APPENDIX D
much as the chrome alum bath, maintains its hardening properties on keeping
and is, therefore, preferable for use in hot weather.
Fixing Bath for Hot Weather
Avoirdupois Metric
Water 64 ozs. 2000 cc.
Hypo 16 ozs. 500 grams
When dissolved, add the following hardening solution:
Water 5 ozs. 150 cc.
Alum (powdered) 1 oz. 28 grams
Sodium sulphite (desiccated) 1 oz. 28 grams
Glacial acetic acid 1 oz. 30 cc.
When using the above solution, fixing will take about double the time (20
minutes as a minimum) required to dissolve the unreduced silver emulsion,
which is determined by noting when the grayish white color disappears from
the back of the negative. After thoroughly fixing, negatives should be washed
for one-half hour in running water to remove all traces of hypo, then stood
on a drying rack so that they will drain from one corner. Films should be
suspended from one corner to dry.
A convenient test for determining whether washing is complete, which mayalso be used for prints, is made as follows:
Test for Completion of Washing
Avoirdupois Metric
Water 8 ozs. 240 cc.
Potassium permanganate 8 grains § gram
Sodium carbonate 10 grains f gram
Allow the excess water to drain from the partially washed negative or print
into a graduate and add a few drops of the above solution. If the color remains
pink, washing has been complete; but if it turns yellowish, hypo is still present.
This is a verj^ sensitive test and is useful where speed is necessary.
Over- and Under-Exposed Negatives, — Underexposed negatives will lack
detail in parts corresponding to the darker regions of the specimen, while over-
exposed will be "flat"; i.e., full of detail without much contrast. Whenever
possible, it is better to repeat the exposure, making another negative giving
double, or half the exposure time, as the case may be, than to attempt to
"doctor" a poor negative. Nothing can be done with underexposure, as detail
lacking in the negative originally cannot be introduced by any chemical process.
Contrast may be increased in overexposed negatives, but the process is uncertain
and the intensified negative is rarely permanent. Repeat the exposure, or
use a contrasty paper when making prints.
Overdeveloped negatives are very dense, requiring a long time in printing.
These may be reduced in the following solution:
APPENDIX D 241
Reducing Solution
Avoirdupois Metric
A. Water 1 oz. 30 cc.
Potassium ferricyanide 15 grains 1 gramB. Water 32 ozs. 1000 cc.
Hypo 1 oz. 28 grams
Mix A and B and immerse the plate in the solution until sufficiently reduced.
Wash thoroughly and dry in the usual manner. The above solutions (A and B)
keep well, but the reducer obtained by mixing A and B will remain active for
only a short time.
Printing. — Prints are made from the negative in the usual way. Use a
constant light source and always place the printing frame at a constant distance
from it (18 inches for a 100 watt bulb). The proper exposure for the print
may easily be estimated from the density of the negative after a few trials.
If many prints are to be made a special printing machine is a good investment.
Satisfactory papers are Azo, Cyco, and Velox. Azo is somewhat slow to
print but is cheap in price and easy to work with, and an excellent paper for
general use. It is made in four grades, Nos. 1 to 4. The latter gives mostcontrast and is recommended for the average negative. Cyco prints morerapidly than Azo and is made in three grades: Contrast, Normal and Soft.
The former is very contrasty, and the latter very soft and intended for very
contrasty negatives. Normal Cyco is for general use and is about equivalent
to No. 3 Azo. Velox is made in four grades in the same order as Azo. It is
more expensive than Azo and has no advantage over it. It is to be rememberedthat "hard" or "contrasty" papers are to be used for "soft" or "flat" nega-
tives, and vice versa. Always use paper with glossy surface.
There is no single developer that will give the best results with all makesof papers. It is safe to use that recommended by the maker of the paper.
For the above mentioned papers, the following may be relied upon to give goodresults.
Make up a stock solution as follows:
Dissolve in the order given:
Avoirdupois Metric
Warm water (distilled) 16 ozs. 500 cc.
Sodium sulphite (desiccated) 1^ ozs. 35 gramsMetal or Elon 30 grains 2 grams
When completely dissolved, add:
Hydrochionone 120 grains 8 gramsSodium carbonate (desiccated) If ozs. 50 gramsPotassium Ijromide 15 grains 1 gramSodium citrate 15 grains 1 gram
Dissolve Elon in water before adding sodium sulphite; otherwise reprecipita-
tion may occur.
242 APPENDIX D
This is a concentrated solution which will keep for months in filled, tightly
corked bottles. For a working solution, dilute with 2 parts water for hard
or contrasty papers or with 4 parts for normal and soft papers. Temperature
of developer should be 65 degrees Fahr.
Contrasty papers should develop quickly, 20 to 40 seconds, while soft and
normal papers will develop more slowly, 40 to 60 seconds. The printing
exposure should be so adjusted that development will be complete in the times
specified. Too short exposure will require long development, giving cold,
bluish tones; too long exposure will cause prints to flash up and darken before
they can be removed from developer, giving muddy oUve tones. If altering
the exposure time does not remedy this, the addition of a few grains of caustic
potash or soda to the developer will remove olive tones, and a few drops of
10 per cent solution of potassium bromide will correct blue tones.
When prints are fixed in the fixing bath given above, 10 minutes are sufficient
provided they are kept in motion. After fixing, wash in running water 30
minutes, or until permanganate test shows absence of hypo. Dry prints on a
ferrotype plate or " squeegee board " by placing them with surface down, covering
with blotters and pressing into firm contact with a print roller. However,
if the wash water is dirty or contains sediment, swab each print clean with a
tuft of wet cotton before placing on ferrotype plate. When dry the prints
may easily be stripped off, and will have a brilliant glossy surface which is
very pleasing and which will show the finest details of the negative. Ferrotype
plates should be kept clean and free from scratches. They may be washed
with soap and water if necessary. Any tendency of prints to stick to the
ferrotype plate may be overcome by rubbing its surface with a drop or two
of three-in-one oil or paraffin dissolved in benzine, and polishing with a tuft
of clean dry cotton or a soft cloth.
Trimming of Prints. — This is most easily done with a knife edge print
trimmer to a size 3| inches square or any other convenient size. Some prefer
a circular shape and this can be done by cutting the dry print with a revolvuig
print trimmer and a metal mask. Care must be used with tliis method to
avoid rough edges on the print. Circular prints may also be made on square
sheets during printing, by placing a mask made of red or black paper between
the negative and the light. If the printing mask is used it should not be placed
between the negative and the paper. In the latter position, fine detail maybe destroyed.
General Precautions. — Have a separate room set aside to be used for the
dark room and for no other purpose. It should be provided with a wide bench
along one wall with sink and running water at one end. A "safe fight "' over
the sink and another at the other end of bench will be convenient, the latter
for loading plate holders. Dust off plates with a soft camel's hair brush before
loading, to prevent pinholes in the negative. Keep tilings in order, with a
place for everything and everything in its place. Store negatives in paper
envelopes with number, description and other data on each one, and with a
catalog so that a given negative can be found quickly when wanted. Cleanli-
APPENDIX D 243
ness is essential. Do not allow dried developer to collect around necks of
bottles. Have a special tray or hard rubber fixing box for the fixing bath anduse it for no other purpose. Never use a hypo tray for developing. Rinsefingers and hands after handling prints in fixing bath before again using the
developer. Hypo is an excellent thing in a fixing bath, but a very bad one in
the developer. If developers or fixing bath get spilled, wipe them up and donot allow dried crystals to blow around the dark room. In warm weather putdeveloping tray into a larger one containing ice water and thus keep solutions
at their proper temperature.
If possible printing should be,done in a separate dark room where an orangeor dark yellow light will suffice. An electric fan is a great convenience for
hastening the drying of negatives and prints.
References
Albert- Sauveur, "Metallography and Heat Treatment of Iron and Steel."
1920, 2nd edition.
F. F. Lucas, "High Power Photomicrography of Metallurgical Specimens,"
Transactions, American Society for Steel Treating, Vol. IV, 1923, page 611.
H. S. George, "Conical Illumination in Metallography," Transactions, AmericanSociety for Steel Treating, Vol. IV, 1923, page 140.
W. L. Patterson, "The Optics of IVIetallography," Transactions, AmericanSociety for Steel Treating, Vol. II, 1921, page 108.
Recommended Practice for Photography as applied to Metallography, Com-mittee E-4, American Society for Testing Materials, Serial designation
E7-23T, 1923.
Eastman Kodak Company, "Photomicrograph}^," 5th edition, 1919.
Walter M. Mitchell, "The Metallurgical Microscope," Forging and Heat
Treating, Vol. IX, 1923, pages 63, 106.
APPENDIX E(a)
STANDARD DEFINITIONS OF TERMS RELATING TOMETALLOGRAPHY*
Serial Designation: E7-27
Issued as Tentative, 1921; Adopted in Amended Form, 1924; Revised, 1927.
Alloy. — A substance, having metallic properties, consisting of two or more
metallic elements, or of metallic and non-metallic elements, which are miscible
with each other when molten, and have not separated into distinct layers
when solid.
Note: Alloys when solid may be composed of eutectics, euteetoids, solid solu-
tions, chemical compounds, or of aggregates of these components with each
other or with pure metals. In the commercial sense, the term "alloy" would also
include the case where some separation into distinct layers had occurred.
Etching Reagent. — A substance or reagent used to reveal the structure
of a metal or alloy causing a difference in the appearance of different constituent
parts or different grains.
Note: This substance is usually a solution of the reagent in water, acid or alkali,
but etching may in some cases be brought out by a differential oxidation produced
by ''heat tinting."
Equiaxed Grain. — A grain which has approximately ecjual dimensions in
all directions.
Note: This term is practically restricted to unstrained metals.
Grain. — A term used for an allotrimorphic ciystal present in metals and
in one-component alloys.
Note: Although a crystal may show division by "twinning," etc., it is regarded
as the grain rather than smaller sub-divisions. In the case of alloys of more than
one component, the crystal which, by its transformation, gave rise to these con-
stituents is taken as the grain when its limits are still discernible; if the limits are
not discernible the individual constituents are considered as grains.
Grain Size. — This is preferably expressed as the number of grains per unit
area of cross-section. The average cross-sectional area of the grain may also
be given or the average dimensions. Grain size of strained material is expressed
* Printed from the American Society for Testing Materials — Standards 1927,
by permission.
244
APPENDIX E (a) 245
by the average number per linear unit in Iwo directions, or bj^ the average
number per unit cross-sectional area, together with the ratio of length to
breadth (L/B).
Note: By the "Intercept" Method for grain count, the number of grains and
fractions of grains along a line of known length on two axes at right angles to each
other are counted. By the "Planimetric'' Method for grain count, the numberof grains and fractions of grains within a definite area are counted.
Macrograph. — A graphic reproduction of any subject which has not been
magnified more than 10 diameters.
Note: When it is desired to indicate that it is a photographic reproduction, the
term "photomacrograph" may be employed.
Magnification. — The ratio of the size of the image to that of the object.
Note: Magnification is generally expressed in "diameters," thus "XlOO" or
" 100 diameters."
Metal. — Any of the metallic elements, either of very high purity or of
ordinary commercial grades.
Note: Brass and many other alloys are metals in the commercial sense, but
alloys in the scientific sen.se.
Metallography. — That branch of science which relates to the constitution
and structure, and their relation to the properties, of metals and alloys.
Micrograph. — A graphic reproduction of any object magnified more than
10 diameters.
Note: When it is desired to indicate that it is a photographic reproduction, the
term "photomicrograph" may be employed.
APPENDIX E(b)
DEFINITIONS OF OTHER METALLOGRAPHIC TERMS
By Prop. H. M. Boylston*
When specimens of iron and steel (and other metals and alloys) are suitably-
polished and etched with dilute acids or other special reagents, certain char-
acteristic crystalline formations are observable under the microscope. In
most cases they correspond (in the case of iron and steel) to various fields on
the iron-carbon equilibrium diagram, shown in Fig. 5. The following defini-
1.
Molten Iron
(Fer Fondu)
8.B.
Cementite
+Pearlite
2 3
Carbon Per Cent
Fig. 5. Iron-Carbon Diagram.
tions of these constituents include their constitution, microstructure, occur-
rence, and normal position in the iron-carbon diagram.
Allotriomorphic Crystals. — When the free development of crystals is
hindered by unfavorable crystallizing conditions, as, for example, contact with
other crystals, likewise in process of formation, the regular external form is
* Prof. Boylston has given the author permission to reproduce these definitions,
published in the "Engineers," 1928.
246
APPENDIX E (b) 247
not preserved and the resulting imperfect crystals are called allotriomorphic
crystals or occasionally "anhedrons" or faceless crystals. They are frequently
called "crystaUine grains" or "grains" (Sauveur).
AUotropy. — That property of certain substances by virtue of which their
physical properties are suddenly and markedly changed at certain temperatures
known as transformation temperatures, without a change in chemical com-
position. Two allotropic forms of carbon are diamond and graphite. The
allotropic forms of iron are thought to be alpha, beta, gamma, delta, although
some doubt the existence of the beta form and some believe that the alpha and
delta allotropic forms are identical. This term should not be confused with
polymorphism, which is the property of some substances by virtue of which
they crystallize in more than one form. Some use these terms a^ synonyms.
1500
248 APPENDIX E (b)
Crystals. — An arrangement of atoms forming small solids of regular
geometrical outlines, such as cubes, octahedra, etc. (Sauveur.)
Dendrites. — Crystalline groups or aggregates of allotriomorphic crystals
arranged in distinct forms usually described as "tree-like," "fern-leaf," "pine-
tree," etc. (Sauveur.)
JEutectic Alloy. — The word eutectic means "well melting." A eutectic
alloy is that alloy in any series which has the lowest melting point of that series;
the melting point is constant and occurs at a temperature known as the eutectic
temperature. Eutectic alloys have a characteristic microstructure consisting
of alternating laminations or a series of regular dots or rods occurring on a
plain background.
\ Eutectoid Steel. — Steel made up exclusively of pearlite or having such a
content of carbon (0.90% in pure iron-carbon alloys, approximately 0.85%
in commercial steels) that it would be made up exclusively of pearlite if slowly
,cooled from above the critical range.
\ Ferrite. — Ferrite is nearly pure iron. It may contain in solid solution
such impurities as carbon (up to 0.05%), silicon (up to 4%), phosphorus (up to
1.7%), nickel, copper, vanadium, molybdenum, tungsten and chromium in
small amounts when in the alpha state. It is thought to exist in four allotropic
forms: alpha, beta, gamma, and delta. Alpha iron is the softest constituent
in iron and steel, and the principal one in ingot iron, wrought iron and low-
carbon steel. It forms the dark lamina3 of pearlite of which it forms 87^%,
by weight. It is found in regions 6, 7, 8A and 8B in Fig. 5. When free,
alpha iron exists as polyhedral grains surrounded by dark networks.
\ Graphite. — Graphite is carbon crystals seen in the form of curved or
spiral plates in gray or mottled cast iron. It is also found in rounded masses
or "rosettes" in malleable cast iron, and in this form also is thought to consist
of minute carbon crystals. It is normal in regions 3, 5, 8A and 8B in Fig. 5
when the alloys are very slowly cooled and especially if much silicon is present.
It is also found in the rosette form, occasionally, in high-carbon tool steels,
especially if the silicon be high (over 0.50%) or if there be any nickel present,
in the absence of chromium. In such cases it is produced by annealing and
\ ruins the steel.
^ Hyper-eutectoid Steel. — Steel which contains more than 0.85% carbon
and hence normally contains some free cementite after slow cooling from above
the critical range.
^ Hypo-eutectoid Steel. — Steel which contains less than 0.85% carbon
and hence normally contains some free ferrite after slow cooling from above
the critical range.
Inclusions. — Solid non-metallic substances mechanically embedded in
metals or alloys.
Manganese sulphide (MnS) occurs in iron and steel containing more than
a trace of sulphur. It appears under the microscope as round (in castings)
or lenticular (in worked metal) dove-gray spots.
/APPENDIX^ E (b) 249
Martensite (constitution disputed) is the principal constituent of hardenedand untempered steels and is harder than austenite, troostite, or sorbite.
Sauveur and others believe it to be an aggregate or mechanical mixture of a
solid solution of carbon in supercooled gamma iron and of a supersaturated
solution of carbon in alpha iron. Under the microscope it is seen as dark
needles arranged indistinctly in equilateral triangles, and at very high mag-nifications, a still darker midrib of troostite (?) is distinguishable.
Neximann Bands. — Mechanical twins appearing as a number of parallel
lines or narrow bands which follow the orientation of the grains of metals.
They are generally produced by sudden deformation of the metal such as
(would result from shock, impact or explosion (Sauveur)
.
JPearlite. — Pearlite is a mechanical mixture (aggregate) of alpha ferrite
and cementite which is the principal constituent of slowly cooled annealed
steels. It is always associated with an excess of ferrite or cementite except in
steels containing between 0.70 and 0.90% carbon (theoretically 0.90% carbon
in pure iron-carbon alloy and about 0.85% in commercial steels). It is normal
in regions 8A and SB, Fig. 5. At low magnification it appears as dark irregular
grains but at high magnifications it occurs as alternating curved, black andwhite lamellae.
Solid Solution (as applied to metals) .— A mixture of metals or metalloids
in the solid state in which the constituents are completely merged in indefinite
proportions.
Sorbite. — Sorbite is a transition stage between troostite and pearlite.
It is believed by most authorities to be an uncoagulated conglomerate of irre-
soluble pearlite with ferrite in hypo-eutectoid and cementite in hyper-eutectoid
steels respectively. It is the principal constituent of air-cooled (normalized
steels) and of hardened steels reheated to 1,112 to 1,292 degrees Fahr. (600 to 700
degrees Cent.). It has no place in the diagram. It etches more rapidly than
pearlite and at low magnifications appears as dark grains (darker than pearlite)
surrounded by ferrite boundaries in hypo-eutectoid and by cementite boundaries
or globules in hyper-eutectoid steels. In steels containing between 0.70 and
0.90% carbon the structure is practically 100% sorbite after air-cooUng. Athigh magnifications, sorbite appears as a mass of mixed black and white dots.
It is harder than pearlite but softer than troostite or martensite.
Steadite. — The binary eutectic of iron and iron phosphide which occurs
in gray cast iron.
Troostite. — Troostite is generally believed to be an extremely fine aggre-
gate of the carbide FesC and alpha iron. In the transformation of austenite
it is the stage following martensite and preceding sorbite. By some it is con-
sidered to be an uncoagulated conglomerate of the transition stages. It is
colored decidedly darker than any other constituent by the ordinary etching
reagents. It generally occurs as dark-colored irregular areas representing
sections through nodules and is generally accompanied by martensite or sorbite
or both. It may exist as membranes surrounding martensite grains. Sauveur
believes it to exist as the midrib in needles of martensite. Sauveur has suggested
250 APPENDIX E (b)
that it may be a solid solution of iron and carbon, probably in the form of the
carbide FesC in non-gamma iron.
Twinning. — The grouping of two or more crystals or parts of a crystal
in such a way that they are symmetrical to each other with respect to a plane
between them (the twinning plane), which plane, however, is not a plane of
symmetry (Sauveur).
APPENDIX E(c)
DEFINITIONS
TENTATIVE DEFINITIONS OF TERMS RELATING TOHEAT TREATMENT OPERATIONS*
(Especially as related to Ferrous Alloys)
Foreword. — 1. During recent years certain confusion has arisen in regard
to the meaning of commonly used heat treating terms. For instance, in one
locaUty or trade any operation of heating and cooling, resulting in a softening
of the material, is being called annealing, whereas in other places to "anneal"
means not primarily "to soften" but to heat above the critical temperature
and cool very slowly. Similar confusion as to meaning and application exists
in regard to other terms and as a result "annealing," "tempering," "normaliz-
ing," etc., are being used by different people to mean widely different things.
2. In any attempt to accurately define the terms commonly used in connec-
tion with heat treatment, the first question to decide and the most important
one is: do the terms relate to the heat treatment operation itself, or to the
results obtained by the treatment? In other words, is the term indicative of
the structure or the condition obtained, or of the operation performed?
3. After careful consideration, it appears most logical and most in keeping
with present day usage to have the terms so defined that they shall mean
definite operations and shall not be considered as referring to the resultant
structures or general conditions.
4. By "critical temperature range," as used in the definitions, is meant
that temperature range illustrated by the diagram given in Fig. 7, taken from
Howe.
Definitions
1. Heat Treatment. — An operation, or combination of operations, involv-
ing the heating and cooling of a metal or an alloy in the solid state.
Note: This is for the purpose of obtaining certain desirable conditions or prop-
erties. Heating and cooling for the sole purpose of mechanical working are excluded
from the meaning of this definition.
2. Quenching. — Immersing to cool.
Note: Immersion may be in liquids, gases or solids.
* These definitions were prepared by a joint committee composed of representa-
tives of the A. S. T. M., S. A. E., and A. S. S. T. Printed from the American Society
for Steel Treating handbook, by permission.
251
252 APPENDIX E (c)
3. Hardening. — Heating and quenching certain iron base alloys from a
temperature either within or above the critical temperature range.
4. Annealing. — Annealing is a heating and cooling operation of a material
in the solid state.
Note {A): Annealing usually implies a relatively slow cooling.
Note (B): Annealing is a comprehensive term. The purpose of such a heat
treatment may be:
(a) To remove gases.
(b) To remove stresses.
(c) To induce softness.
(d) To alter ductility, toughness, electrical, magnetic or other physical properties.
(e) To refine the crystalline structure.
Acl Ac 3-2-1
Fig. 8
In annealing, the temperature of the operation and the rate of cooling depend
upon the material being heat treated and the PURPOSE of the treatment.
Certain specific heat treatments coming under the comprehensive term
"annealing" are:
A. Normalizing. — Heating iron base alloys above the critical temperature
range followed by cooling to below that range in still air at ordinary temperature.
Note: In the case of hyper-eutectoid steel, it is often desirable to heat above the
Accm line, as shown in Fig. 8.
B. Spheroidizing. — Prolonged heating of iron base alloys at a temperature
in the neighborhood of, but generally slightly below, the critical temperature
range, usually followed by relatively slow cooling.
Note: (a) In the case of small objects of high carbon steels, the spheroidizing
result is achieved more rapidly by prolonged heating to temperatures alternately
within and slightly below the critical temperature range.
(b) The object of this heat treatment is to produce a globular condition of the
carbide.
C. Tempering (also termed Drawing). — Reheating, after hardening to
some temperature below the critical temperature range followed by anj^ rate
of cooling.
Note: (a) Although the terms "tempering" and "drawing" are practically
synonymous as used in commercial practice, the term "tempering" is preferred.
APPENDIX E (c) 253
(6) Tempering, meaning the operation of hardening followed by reheating, is a
usage which is illogical and confusing in the present state of the art of heat treating
and should be discouraged.
D. Malleablizing. — Malleablizing is a type of annealing operation with
slow cooling whereby combined carbon in white cast iron is transformed to
temper carbon and in some cases the carbon is entirely removed from the
iron.
Note: Temper carbon is free carbon in the form of rounded nodules made up of
an aggregate of minute crystals.
E. Graphitizing. — Graphitizing is a type of annealing of cast iron whereby
some or all of the combined carbon is transformed to free or uncombined carbon.
5. Carburizing (Cementation). — Adding carbon to iron-base alloys by
heating the metal below its melting point in contact with carbonaceous material.
Note: The term "carbonizing" used in this sense is undesirable and its use
should be discouraged.
6. Case-Hardening. — Carburizing and subsequent hardening by suitable
heat treatment, all or part of the surface portions of a piece of iron-base alloy.
Case. — That portion of a carburized iron-base alloy article in which the
carbon content has been substantially increased.
Core. — That portion of a carburized iron-base alloy article in which the
carbon content has not been substantially increased.
Note: The terms "case " and " core " refer to both case-hardening and carburizing.
7. Cyaniding. — Surface hardening of an iron-base alloy article or portion
of it by heating at a suitable temperature in contact with a cyanide salt, fol-
lowed by quenching.
d
p(
DUE DATE
TN 693.I7R37
3 9358 00014057 1
TN6 9317R37
Reedy Everett Lenox*Photomicrographs of iron and steely
by Everett L. Reed ••• with a forewordby Dr. Albert Sauveur ••• New York, J.Wiley S sonsT i nc • ; London, Chapman i>
Hall, limited [cl&29]2 p. I., lil-xx, 253 p. illus«,
diagrs. 24 cm»
14057
MPMU 18 MAY 7 7 168S280 NEDDbp i9-2112